ONE GAS, INC., 10-K filed on 2/20/2025
Annual Report
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Audit Information
 12 Months Ended
Dec. 31, 2024
Document Information [Line Items]  
Auditor Name PricewaterhouseCoopers LLP
Auditor Location Tulsa, Oklahoma
Auditor Firm ID 238
v3.25.0.1
Cover Page - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Feb. 14, 2025
Jun. 30, 2024
Document Information [Line Items]      
Entity Central Index Key 0001587732    
Current Fiscal Year End Date --12-31    
Document Fiscal Year Focus 2023    
Document Fiscal Period Focus FY    
Amendment Flag false    
Entity Information [Line Items]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2024    
Document Transition Report false    
Entity File Number 001-36108    
Entity Registrant Name ONE Gas, Inc.    
Entity Incorporation, State or Country Code OK    
Entity Tax Identification Number 46-3561936    
Entity Address, Address Line One 15 East Fifth Street    
Entity Address, City or Town Tulsa,    
Entity Address, State or Province OK    
Entity Address, Postal Zip Code 74103    
City Area Code (918)    
Local Phone Number 947-7000    
Title of 12(b) Security Common Stock, par value $0.01 per share    
Trading Symbol OGS    
Security Exchange Name NYSE    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag true    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company false    
Entity Public Float     $ 3,500
Entity Common Stock, Shares Outstanding   59,877,552  
Documents Incorporated by Reference
Portions of the definitive proxy statement to be delivered to shareholders in connection with the Annual Meeting of Shareholders to be held May 22, 2025, are incorporated by reference in Part III.
    
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STATEMENTS OF INCOME - USD ($)
shares in Thousands, $ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Regulated Operating Revenue $ 2,083,558 $ 2,371,990 $ 2,578,005
Cost of natural gas 778,333 1,134,510 1,459,087
Operating expenses      
Operations and maintenance 530,111 508,399 472,265
Depreciation and amortization 296,699 279,830 228,479
General taxes 79,371 71,661 68,217
Total operating expenses 906,181 859,890 768,961
Operating income 399,044 377,590 349,957
Other Nonoperating Income (Expense) 7,427 9,476 (4,183)
Interest expense, net (147,235) (115,339) (77,506)
Income before income taxes 259,236 271,727 268,268
Income taxes (36,386) (40,495) (46,526)
Net income $ 222,850 $ 231,232 $ 221,742
Earnings per share      
Basic $ 3.92 $ 4.16 $ 4.09
Diluted $ 3.91 $ 4.14 $ 4.08
Weighted Average Number of Shares Outstanding, Basic [Abstract]      
Basic 56,826 55,600 54,207
Weighted Average Number of Shares Outstanding, Diluted [Abstract]      
Diluted 57,033 55,860 54,338
Common Stock, Dividends, Per Share, Declared $ 2.64 $ 2.60 $ 2.48
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STATEMENTS OF COMPREHENSIVE INCOME - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Net income $ 222,850 $ 231,232 $ 221,742
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax 960 (478) 5,823
OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax 96 0 0
Other comprehensive income (loss) 1,056 (478) 5,823
Comprehensive income $ 223,906 $ 230,754 $ 227,565
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STATEMENTS OF COMPREHENSIVE INCOME Parenthetical - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Statement of Comprehensive Income [Abstract]      
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax $ (281) $ 140 $ (1,705)
OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment, Tax $ (25) $ 0 $ 0
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BALANCE SHEETS - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
Property, plant and equipment    
Property, plant and equipment $ 9,124,134 $ 8,468,967
Accumulated depreciation and amortization 2,478,261 2,333,755
Net property, plant and equipment 6,645,873 6,135,212
Current assets    
Cash and Cash Equivalents 57,995 18,835
Restricted Cash and Cash Equivalents 20,542 20,552
Cash, cash equivalents, restricted cash and restricted cash equivalents 78,537 39,387
Accounts receivable, net 408,448 347,864
Materials and supplies 91,662 77,649
Income Taxes Receivable 53,624 3,947
Natural Gas in Storage 161,184 187,097
Regulatory assets, Current 101,210 75,308
Other current assets 35,216 33,952
Total current assets 929,881 765,204
Goodwill and other assets    
Regulatory assets, Noncurrent 278,006 287,906
Other Intangible Assets, Net 265,951 293,619
Goodwill 157,953 157,953
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position 42,882 36,482
Other assets 105,025 94,618
Total goodwill and other assets 849,817 870,578
Total assets 8,425,571 7,770,994
Equity and long-term debt    
Common stock, $0.01 par value: authorized 250,000,000 shares; issued and outstanding 59,876,861 shares at December 31, 2024; issued and outstanding 56,545,924 shares at December 31, 2023 599 565
Paid-in Capital 2,294,469 2,028,755
Retained earnings 809,606 737,739
Accumulated other comprehensive loss (126) (1,182)
Total equity 3,104,548 2,765,877
Other Long-Term Debt, Noncurrent 2,131,718 1,877,895
Securitized utility tariff bonds, excluding current maturities, net of issuance costs 253,568 282,506
Long-Term Debt, Excluding Current Maturities, Total 2,385,286 2,160,401
Total equity and long-term debt 5,489,834 4,926,278
Current liabilities    
Long-term Debt, Current Maturities 14 772,984
Current maturities of securitized utility tariff bonds 28,956 27,430
Short-term debt 914,600 88,500
Accounts payable 261,321 278,056
Accrued taxes other than income 75,608 68,793
Regulatory Liability, Current 22,525 66,901
Customer deposits 56,243 62,187
Other current liabilities 99,009 112,370
Total current liabilities 1,458,276 1,477,221
Deferred credits and other liabilities    
Deferred income taxes 891,738 752,068
Regulatory Liability, Noncurrent 467,563 500,478
Other deferred credits 118,160 114,949
Total deferred credits and other liabilities 1,477,461 1,367,495
Commitments and contingencies
Total liabilities and equity $ 8,425,571 $ 7,770,994
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BALANCE SHEETS Parenthetical - $ / shares
Dec. 31, 2024
Dec. 31, 2023
Common Stock, Par or Stated Value Per Share $ 0.01 $ 0.01
Common Stock, Shares Authorized 250,000,000 250,000,000
Common Stock, Shares, Issued 59,876,861 56,545,924
Common Stock, Shares, Outstanding 59,876,861 56,545,924
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STATEMENTS OF CASH FLOWS - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Operating activities      
Net income $ 222,850 $ 231,232 $ 221,742
Adjustments to reconcile net income to net cash provided by operating activities:      
Depreciation and amortization 296,699 279,830 228,479
Deferred income taxes 106,522 24,773 (22,034)
Share-based compensation expense 13,733 12,184 10,741
Provision for doubtful accounts 6,705 9,698 6,003
Proceeds from Securitization Bonds, Operating Activities 0 197,366 1,330,582
Changes in assets and liabilities:      
Accounts receivable (67,289) 196,272 (213,656)
Materials and supplies (14,013) (6,776) (15,981)
Proceeds from Income Tax Refunds (49,677) (3,947) 0
Natural gas in storage 25,913 82,108 (89,559)
Payments for Removal Costs (58,952) (62,023) (47,032)
Accounts payable (15,014) (90,046) 85,915
Accrued taxes other than income 6,815 (9,559) 11,317
Customer deposits (5,944) 4,333 (4,600)
Increase (Decrease) In Regulatory Assets And Liabilities Current, net (90,829) 7,249 52,417
Increase (Decrease) In Regulatory Assets And Liabilities Noncurrent, net 19,354 38,869 53,992
Increase (Decrease) in Other Current Assets and Liabilities, Net (17,091) 30,017 (23,377)
Increase (Decrease) in Other Noncurrent Assets and Liabilities, Net (11,371) (2,048) (14,107)
Cash provided by operating activities 368,411 939,532 1,570,842
Investing activities      
Capital expenditures (703,165) (666,634) (609,486)
Payments for Other Investing Activities (10,402) (8,508) (8,632)
Proceeds from Sale of Other Assets, Investing Activities 6,072 5,499 4,008
Cash used in investing activities (707,495) (669,643) (614,110)
Financing activities      
Borrowings (repayments) of short-term debt, net 826,100 (463,500) 58,000
Proceeds from Issuance of Senior Long-Term Debt 253,467 299,583 297,591
Issuance of securitized utility tariff bonds, net of discounts 0 0 335,931
Payments of Debt Issuance Costs (2,193) (2,508) (8,567)
Repayments of Other Long-Term Debt (773,013) 0 1,627,000
Repayment of securitized utility tariff bonds (27,939) (20,716) 0
Proceeds from Issuance of Common Stock 252,379 85,259 133,711
Dividends paid (149,456) (144,094) (133,954)
Payment, Tax Withholding, Share-based Payment Arrangement (1,111) (2,653) (3,169)
Cash used in financing activities 378,234 (248,629) (947,457)
Change in cash and cash equivalents 39,150 21,260 9,275
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Beginning Balance 39,387 18,127 8,852
Cash, cash equivalents, restricted cash and restricted cash equivalents at end of period 78,537 39,387 18,127
Interest Paid, Excluding Capitalized Interest 148,987 80,726 84,871
Income Tax Paid, State and Local, after Refund Received 366 769 621
Income Tax Paid, Oklahoma, after Refund Received (4,546) 1,571 5,300
Income Tax Paid, Federal, after Refund Received $ (16,280) $ 18,504 $ 61,500
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STATEMENT OF CHANGES IN EQUITY - USD ($)
$ in Thousands
Total
Common Stock [Member]
Paid-in Capital [Member]
Retained Earnings [Member]
Accumulated Other Comprehensive Income (Loss) [Member]
Shares issued, beginning balance at Dec. 31, 2021   53,633,210      
Common stock issued, shares   1,716,744      
Shares issued, ending balance at Dec. 31, 2022   55,349,954      
Equity, beginning balance at Dec. 31, 2021 $ 2,349,532 $ 536 $ 1,790,362 $ 565,161 $ (6,527)
Net income 221,742 0 0 221,742 0
Other comprehensive income (loss) 5,823 0 0 0 5,823
Common stock issued, value $ 141,283 17 141,266 0 0
Dividends paid per share of stock $ 2.48        
Dividends, Common Stock $ (133,954) 0 1,086 (135,040) 0
Equity, ending balance at Dec. 31, 2022 $ 2,584,426 $ 553 1,932,714 651,863 (704)
Common stock issued, shares   1,195,970      
Shares issued, ending balance at Dec. 31, 2023 56,545,924 56,545,924      
Net income $ 231,232 $ 0 0 231,232 0
Other comprehensive income (loss) (478) 0 0 0 (478)
Common stock issued, value $ 94,791 12 94,779 0 0
Dividends paid per share of stock $ 2.60        
Dividends, Common Stock $ (144,094) 0 1,262 (145,356) 0
Equity, ending balance at Dec. 31, 2023 $ 2,765,877 $ 565 2,028,755 737,739 (1,182)
Common stock issued, shares   3,330,937      
Shares issued, ending balance at Dec. 31, 2024 59,876,861 59,876,861      
Net income $ 222,850 $ 0 0   0
Other comprehensive income (loss) 1,056 0 0 0 1,056
Common stock issued, value $ 264,221 34 264,187 0 0
Dividends paid per share of stock $ 2.64        
Dividends, Common Stock $ (149,456) 0 1,527 (150,983) 0
Equity, ending balance at Dec. 31, 2024 $ 3,104,548 $ 599 $ 2,294,469 $ 809,606 $ (126)
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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Notes)
 12 Months Ended
Dec. 31, 2024
Accounting Policies [Abstract]  
SIGNIFICANT ACCOUNTING POLICIES SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Basis of Presentation - The consolidated financial statements include the accounts of our natural gas distribution business as set forth in “Organization and Nature of Operations” below. All significant balances and transactions between our subsidiaries have been eliminated.
Organization and Nature of Operations - We provide natural gas distribution services to approximately 2.3 million customers in Oklahoma, Kansas and Texas through our three divisions, Oklahoma Natural Gas, Kansas Gas Service and Texas Gas Service, respectively. We primarily serve residential, commercial and transportation customers in all three states. We are a corporation incorporated under the laws of the state of Oklahoma, and our common stock is listed on the NYSE under the trading symbol “OGS.”
Segments - We operate in one reportable business segment: regulated public utilities that deliver natural gas primarily to residential, commercial and transportation customers. We define reportable business segments as components of an organization for which discrete financial information is available and operating results are evaluated on a regular basis by the CODM in order to assess performance and allocate resources. Our CODM is our Chief Executive Officer. Characteristics of our organization that were relied upon in making this determination include the similar nature of services we provide, the functional alignment of our organizational structure, and the reports that are regularly reviewed by the CODM for the purpose of assessing performance and allocating resources. Our management is functionally aligned and centralized, with performance evaluated based upon results of the entire distribution business. Capital allocation decisions are driven by asset integrity management, operating efficiency, growth opportunities and government-requested pipeline relocations, not geographic location or regulatory jurisdiction.

In 2024, 2023 and 2022, we had no single external customer from which we received 10 percent or more of our gross revenues.
Revenues - We recognize revenue from contracts with customers to depict the transfers of goods and services to customers at an amount that we expect to be entitled to receive in exchange for these goods and services. Our sources of revenue are disaggregated by natural gas sales, transportation revenues, and miscellaneous revenues, which are primarily one-time service fees, that meet the requirements of ASC 606. Certain revenues that do not meet the requirements of ASC 606 are classified as other revenues in our Notes to Consolidated Financial Statements in this Annual Report.

Our natural gas sales to customers and transportation revenues represent revenues from contracts with customers through implied contracts established by our tariffs approved by regulatory authorities. Our customers receive the benefits of our performance when the commodity is delivered to the customer. The performance obligation is satisfied over time as the customer receives the natural gas.

For deliveries of natural gas, customers are billed on a monthly cycle. We recognize revenues upon the delivery of natural gas or services rendered to customers. The billing cycles for customers do not necessarily coincide with the accounting periods used for financial reporting purposes. We accrue unbilled revenues for natural gas that has been delivered but not yet billed at the end of an accounting period. We use the invoice method practical expedient, where we recognize revenue for volumes delivered for which we have a right to invoice. Our estimate of accrued unbilled revenue is based on a percentage estimate of amounts unbilled each month, which is dependent upon a number of factors, some of which require management’s judgment. These factors include customer consumption patterns and the impact of weather on usage. The accrued unbilled natural gas sales revenue is included in accounts receivable on our consolidated balance sheets.

Our miscellaneous revenues from contracts with customers represent implied contracts established by our tariff rates approved by the regulatory authorities and include miscellaneous utility services with the performance obligation satisfied at a point in time when services are rendered to the customer.

Total other revenues consist of revenues associated with regulatory mechanisms that do not meet the requirements of ASC 606 as revenue from contracts with customers, but authorize us to accrue revenues earned based on tariffs approved by regulatory authorities. Other revenues - natural gas sales primarily relate to the WNA mechanism in Kansas. This mechanism adjusts our revenues earned for the variance between actual and normal HDDs. This mechanism can have either positive
(warmer than normal) or negative (colder than normal) effects on revenues.
We collect and remit other taxes on behalf of governmental authorities, and we record these amounts in accrued taxes other than income in our consolidated balance sheets. See Note 2 for additional discussion of revenues.
Use of Estimates - The preparation of our consolidated financial statements and related disclosures in accordance with GAAP requires us to make estimates and assumptions with respect to values or conditions that cannot be known with certainty that affect the reported amount of assets and liabilities, and the disclosure of contingent assets and liabilities at the date of the consolidated financial statements. These estimates and assumptions also affect the reported amounts of revenue and expenses during the reporting period. Items that may be estimated include, but are not limited to, the economic useful life of assets, fair value of assets and liabilities, provisions for doubtful accounts receivable, unbilled revenues for natural gas delivered but for which meters have not been read, natural gas purchased but for which no invoice has been received, provision for income taxes, including any deferred income tax valuation allowances, the results of litigation and various other recorded or disclosed amounts.

We evaluate these estimates on an ongoing basis using historical experience and other methods we consider reasonable based on the particular circumstances. Nevertheless, actual results may differ significantly from the estimates. Any effects on our financial position or results of operations from revisions to these estimates are recorded in the period when the facts that give rise to the revision become known.
Cost of Natural Gas - Cost of natural gas includes commodity purchases, fuel, storage, transportation, financial derivatives, and other gas purchase costs recovered through our cost of natural gas regulatory mechanisms and does not include an allocation of general operating costs or depreciation and amortization. These cost of natural gas regulatory mechanisms provide a method of recovering natural gas costs on an ongoing basis without a profit. See Note 3 for additional discussion of purchased gas cost recoveries.
Cash, Cash Equivalents and Restricted Cash and Restricted Cash Equivalents - Cash equivalents and restricted cash equivalents consist of highly liquid investments, which are readily convertible into cash and have original maturities of three months or less. At December 31, 2024, we held $45.4 million in highly liquid investments. Highly liquid investments were not material at December 31, 2023. Restricted cash consists of funds that are contractually or legally restricted as to usage or withdrawal and have been presented separately from cash and cash equivalents on our consolidated balance sheets. Restricted cash and restricted cash equivalents accounts were established for payment of Securitized Utility Tariff Bond issuance costs and payment of debt service on those bonds.
Property, Plant and Equipment - Our properties are stated at cost, which includes direct construction costs such as direct labor, materials, burden and AFUDC. Generally, the cost of our property retired or sold, plus removal costs, less salvage, is charged to accumulated depreciation. Gains and losses from sales or retirement of an entire operating unit or system of our properties are recognized in income. Maintenance and repairs are charged directly to expense.

AFUDC represents the cost of borrowed funds used to finance construction activities. We capitalize interest costs during the construction or upgrade of qualifying assets. Capitalized interest is recorded as a reduction to interest expense, net.

Our properties are depreciated using the straight-line method over their estimated useful lives. Generally, we apply composite depreciation rates to functional groups of property having similar economic circumstances. We periodically conduct depreciation studies to assess the economic lives of our assets. These depreciation studies are completed as a part of our regulatory proceedings, and the changes in economic lives, if applicable, are implemented prospectively when the new rates are approved by our regulators and become effective. Changes in the estimated economic lives of our property, plant and equipment could have a material effect on our financial position, results of operations or cash flows.

Property, plant and equipment on our consolidated balance sheets includes construction work in process for capital projects that have not yet been placed in service and therefore are not being depreciated. Assets are transferred out of construction work in process when they are substantially complete and ready for their intended use.

See Note 14 for additional information regarding our property, plant and equipment.
Accounts Receivable, Net - Accounts receivable represent valid claims against nonaffiliated customers for natural gas sold or services rendered. We assess the creditworthiness of our customers. Those customers who do not meet minimum standards may be required to provide security, including deposits and other forms of collateral, when appropriate and allowed by our tariffs. With approximately 2.3 million customers across three states, we are not exposed materially to a concentration of credit risk. We maintain an allowance for doubtful accounts based upon factors surrounding the credit risk of customers, historical trends, consideration of the current environment and other information. We recover natural gas costs related to accounts written off
when they are deemed uncollectible through the purchased-gas cost adjustment mechanisms in each of our jurisdictions. At December 31, 2024 and 2023, our allowance for doubtful accounts was $14.9 million and $16.1 million, respectively.
Inventories - Natural gas in storage is accounted for on the basis of weighted-average cost. Materials and supplies inventories are stated at the lower of weighted-average cost or net realizable value.
Leases - We determine if an arrangement is a lease at inception if the contract conveys the right to control the use and obtain substantially all the economic benefits from the use of an identified asset for a period of time in exchange for consideration. We identify a lease as a finance lease if the agreement includes any of the following criteria: transfer of ownership by the end of the lease term; an option to purchase the underlying asset that the lessee is reasonably certain to exercise; a lease term that represents 75 percent or more of the remaining economic life of the underlying asset; a present value of lease payments and any residual value guaranteed by the lessee that equals or exceeds 90 percent of the fair value of the underlying asset; or an underlying asset that is so specialized in nature that there is no expected alternative use to the lessor at the end of the lease term. A lease that does not meet any of these criteria is considered an operating lease.

Lease right-of-use assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. Right-of-use assets and liabilities are recognized at the commencement date of a lease based on the present value of lease payments over the lease term. Our lease terms may include options to extend or terminate the lease. We include these extension or termination options in the determination of the lease term when it is reasonably certain that we will exercise that option. We have lease agreements with lease and non-lease components, which are accounted for separately. Additionally, for certain office equipment leases, we apply a portfolio approach to effectively account for the operating lease right-of-use assets and liabilities. We do not recognize leases having a term of less than one year in our consolidated balance sheets.

For purposes of determining the present value of the lease payments, we use a lease’s implicit interest rate when readily determinable. As most of our leases do not provide an implicit interest rate, we use an incremental borrowing rate based on available information at the commencement of the lease. Lease cost for operating leases is recognized on a straight-line basis over the lease term. See Note 6 for additional information regarding our leases.
Derivatives and Risk Management Activities - We record all derivative instruments at fair value, with the exception of certain commodity purchase contracts for which we have chosen the normal purchase normal sale election as they are expected to result in physical delivery. The accounting for changes in the fair value of a derivative instrument depends on whether it has been designated and qualifies as part of a hedging relationship and, if so, the reason for holding it, or if regulatory requirements impose a different accounting treatment.

If certain conditions are met, we may elect to designate a derivative instrument as a hedge of exposure to changes in fair values or cash flows. We have not elected to designate any of our derivative instruments as hedges.

The table below summarizes the various ways in which we account for our derivative instruments and the impact on our consolidated financial statements:
  Recognition and Measurement
Accounting Treatment Balance Sheet Income Statement
Normal purchases and normal sales-Fair value not recorded-Change in fair value not recognized in earnings
Mark-to-market-Recorded at fair value-Change in fair value recognized in, and recoverable through, the purchased-gas cost adjustment mechanisms

See Note 16 for additional information regarding our economic hedging activities using derivatives.
Fair Value Measurements - We define fair value as the price that would be received from the sale of an asset or the transfer of a liability in an orderly transaction between market participants at the measurement date. We use the market and income approaches to determine the fair value of our assets and liabilities and consider the markets in which the transactions are executed. We measure the fair value of a group of financial assets and liabilities consistent with how a market participant would price the net risk exposure at the measurement date.
Fair Value Hierarchy - At each balance sheet date, we utilize a fair value hierarchy to classify fair value amounts recognized or disclosed in our consolidated financial statements based on the observability of inputs used to estimate such fair value. The levels of the hierarchy are described below:

•Level 1 - Unadjusted quoted prices in active markets for identical assets or liabilities;
•Level 2 - Significant observable pricing inputs other than quoted prices included within Level 1 that are, either directly or indirectly, observable as of the reporting date. Essentially, this represents inputs that are derived principally from or corroborated by observable market data; and
•Level 3 - May include one or more unobservable inputs that are significant in establishing a fair value estimate. These unobservable inputs are developed based on the best information available and may include our own internal data.

We recognize transfers into and out of the levels as of the end of each reporting period.

Determining the appropriate classification of our fair value measurements within the fair value hierarchy requires management’s judgment regarding the degree to which market data is observable or corroborated by observable market data. We categorize derivatives for which fair value is determined using multiple inputs within a single level, based on the lowest level input that is significant to the fair value measurement in its entirety. See Note 16 for additional information regarding our fair value measurements.
Impairment of Goodwill and Long-Lived Assets - We assess our goodwill for impairment at least annually as of July 1, unless events or a change in circumstances indicate an impairment may have occurred before that time. As part of our goodwill impairment test, we first assess qualitative factors (including macroeconomic conditions, industry and market considerations, cost factors and overall financial performance) to determine whether it is more likely than not that our fair value is less than the carrying amount of our net assets. If further testing is necessary or a quantitative test is elected to refresh our recurring qualitative assessment, we perform a quantitative impairment test for goodwill.

Our impairment assessment is performed by comparing our fair value with our book value, including goodwill. If the fair value is less than the book value, an impairment is measured by the amount of our carrying value that exceeds fair value, not to exceed the carrying amount of our goodwill.

To estimate fair value, we use two generally accepted valuation approaches, an income approach and a market approach, using assumptions consistent with a market participant’s perspective. Under the income approach, we use anticipated cash flows over a period of years plus a terminal value and discount these amounts to their present value using appropriate discount rates. Under the market approach, we apply acquisition multiples to forecasted cash flows. The acquisition multiples used are consistent with historical market transactions. The forecasted cash flows are based on average forecasted cash flows over a period of years.

Our goodwill impairment analysis performed in 2024 and 2023 utilized a qualitative assessment and did not result in any impairment indicators, nor did our analysis reflect our reporting unit at risk. Subsequent to July 1, 2024, no event has occurred indicating that it is more likely than not that our fair value is less than the carrying value of our net assets.

We assess our long-lived assets for impairment whenever events or changes in circumstances indicate that an asset’s carrying amount may not be recoverable. An impairment is indicated if the carrying amount of a long-lived asset exceeds the sum of the undiscounted future cash flows expected to result from the use and eventual disposition of the asset. If an impairment is indicated, we record an impairment loss equal to the difference between the carrying value and the fair value of the long-lived asset. We determined that there were no material asset impairments in 2024, 2023 or 2022.
Securitized Intangible Asset - On November 18, 2022, KGSS-I acquired the Securitized Utility Tariff Property from Kansas Gas Service for $327.4 million. The Securitized Utility Tariff Property is classified as a securitized intangible asset on our consolidated balance sheets. This securitized intangible asset will be amortized over 10 years, the estimated period needed to collect the required amounts from Kansas Gas Service’s customers to service the Securitized Utility Tariff Bonds. The amortization expense related to the securitized intangible asset will be included in depreciation and amortization expense in our consolidated statements of income. For the years ended December 31, 2024 and 2023, we recorded $27.7 million and $30.2 million, respectively, of amortization expense related to the securitized intangible asset. At the end of its life, this securitized intangible asset will have no residual value. See Note 5 for additional information about the Securitized Utility Tariff Bonds.

Finite-lived intangible assets are stated at cost, net of accumulated amortization, which is recorded on a straight-line or accelerated basis over the life of the asset. We review amortizable intangible assets for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. If such a review should indicate that
the carrying amount of amortizable intangible assets is not recoverable, we reduce the carrying amount of such assets to fair value.
Regulation - We are subject to the rate regulation and accounting requirements of the OCC, KCC, RRC and various municipalities in Texas. We follow the accounting and reporting guidance for regulated operations, including evaluating regulatory decisions to determine appropriate revenue recognition, cost deferrals and recoverability for regulatory assets and refund requirements for regulatory liabilities. During the ratemaking process, regulatory authorities set the framework for what we can charge customers for our services and establish the manner that our costs are accounted for, including allowing us to defer recognition of certain costs and permitting recovery of the amounts through rates over time, as opposed to expensing such costs as incurred. Examples include weather normalization, unrecovered purchased-gas costs, extraordinary costs associated with Winter Storm Uri, pension and postemployment benefit costs and ad-valorem taxes. This allows us to stabilize rates over time rather than passing such costs on to the customer for immediate recovery. Actions by regulatory authorities could have an effect on the amount recovered from customers. Any difference in the amount recoverable and the amount deferred is recorded as income or expense at the time of the regulatory action. A write-off of regulatory assets and costs not recovered may be required if all or a portion of the regulated operations have rates that are no longer:

•established by independent regulators;
•designed to recover our costs of providing regulated services; and
•set at levels that will recover our costs when considering the demand and competition for our services.

Should recovery cease due to regulatory actions, certain of these assets may no longer meet the criteria for recognition and accordingly, a write-off of regulatory assets and stranded costs may be required. There were no write-offs of regulatory assets resulting from the failure to meet the criteria for capitalization during 2024, 2023 and 2022.

See Note 3 for additional information regarding our regulatory assets and liabilities.
Pension and Other Postemployment Employee Benefits - We have defined benefit pension plans covering eligible employees, all of which are closed to new participants. We also sponsor welfare plans that provide other postemployment medical and life insurance benefits to eligible employees who retire with at least five years of service. To calculate the costs and liabilities related to our plans, we utilize an outside actuarial consultant, which uses statistical and other factors to anticipate future events. These factors include assumptions about the discount rate, expected return on plan assets, rate of future compensation increases, age and mortality and employment periods. We use tables issued by the Society of Actuaries to estimate mortality rates. In determining the projected benefit obligations and costs, assumptions can change from period to period and may result in material changes in the cost and liabilities we recognize.
Income Taxes - Deferred income taxes are recorded for the difference between the financial statement and income tax basis of assets and liabilities and carryforward items, based on income tax laws and rates existing at the time the temporary differences are expected to reverse. The effect on deferred income taxes of a change in tax rates is deferred and amortized for operations regulated by the OCC, KCC, RRC and various municipalities in Texas, if, as a result of an action by a regulator, it is probable that the effect of the change in tax rates will be recovered from or returned to customers through future rates. We continue to amortize previously deferred investment tax credits for ratemaking purposes over the periods prescribed by our regulators.

A valuation allowance for deferred income tax assets is recognized when it is more likely than not that some or all of the benefit from the deferred income tax asset will not be realized. To assess that likelihood, we use estimates and judgment regarding our future taxable income, as well as the jurisdiction in which such taxable income is generated, to determine whether a valuation allowance is required. Such evidence can include our current financial position, our results of operations, both actual and forecasted, the reversal of deferred income tax liabilities, as well as the current and forecasted business economics of our industry. We had no valuation allowance at December 31, 2024 and 2023.

We utilize a more-likely-than-not recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position that is taken or expected to be taken in a tax return. We reflect penalties and interest as part of income tax expense as they become applicable for tax provisions that do not meet the more-likely-than-not recognition threshold and measurement attribute. There were no material uncertain tax positions at December 31, 2024 and 2023.

Changes in tax laws or tax rates are recognized in the financial reporting period that includes the enactment date.

See Note 12 for additional information regarding income taxes.
Asset Retirement Obligations - Asset retirement obligations represent legal obligations associated with the retirement of long-lived assets that result from the acquisition, construction, development and/or normal use of the asset. Certain long-lived assets that comprise our natural gas distribution systems, primarily our pipeline assets, are subject to agreements or regulations that give rise to an asset retirement obligation for removal or other disposition costs associated with retiring the assets in place upon the discontinued use of the natural gas distribution system. We recognize the fair value of a liability for an asset retirement obligation in the period when it is incurred if a reasonable estimate of the fair value can be made. We are not able to estimate reasonably the fair value of the asset retirement obligations for portions of our assets because the settlement dates are indeterminable given our expected continued use of the assets with proper maintenance. We expect our natural gas distribution systems will continue in operation for the foreseeable future. Based on our proximity to significant natural gas reserves and infrastructure and the widespread use of natural gas for heating and cooking activities by residential and commercial customers in our service areas, we expect supply and demand to exist for the foreseeable future.

In accordance with long-standing regulatory treatment, we collect through rates the estimated costs of removal on certain regulated properties through depreciation expense as a portion of the net salvage value component of our composite deprecation rates, with a corresponding credit to accumulated depreciation and amortization. These removal costs collected through our rates include costs attributable to legal and nonlegal removal obligations. These costs are addressed prospectively in depreciation rates in each general rate order.

For financial reporting purposes, if the removal costs collected have exceeded our removal costs incurred, we estimate a regulatory liability using current rates since the last general rate order in each of our jurisdictions. At December 31, 2024 and 2023, we have recorded a regulatory liability, as our removal costs incurred are less than amounts collected through our depreciation rates in one of our service territories. Significant uncertainty exists regarding the recording of these regulatory liabilities, pending, among other issues, clarification of regulatory intent. We continue to monitor the regulatory requirements, and the regulatory liabilities incurred may be adjusted as more information is obtained. To the extent these estimated liabilities are adjusted, such amounts will be reclassified between accumulated depreciation and amortization and regulatory liabilities on our balance sheet and therefore will not have an impact on earnings.
Contingencies - Our accounting for contingencies covers a variety of business activities, including contingencies for legal and environmental exposures. We accrue these contingencies when our assessments indicate that it is probable that a liability has been incurred or an asset will not be recovered and an amount can be estimated reasonably. We expense legal fees as incurred and base our legal liability estimates on currently available facts and our estimates of the ultimate outcome or resolution. Accruals for the estimated cost of environmental remediation obligations generally are recognized no later than the completion of a remediation feasibility study. Recoveries of environmental remediation costs from other parties are recorded as assets when their receipt is deemed probable. Actual results may differ from our estimates resulting in an impact, positive or negative, on earnings.

See Note 15 for additional information regarding contingencies.
Share-Based Payments - We expense the fair value of share-based payments net of estimated forfeitures. We estimate forfeiture rates based on historical forfeitures under our share-based payment plans.
Earnings per share - Basic EPS is calculated by dividing net income by the daily weighted-average number of common shares outstanding during the periods presented, which includes fully vested stock awards that have not yet been issued as common stock. Diluted EPS is based on shares outstanding for the calculation of basic EPS, plus unvested stock awards granted under our compensation plans and equity forward sale agreements, but only to the extent these instruments dilute earnings per share.
Reclassifications - Reclassifications have been made in the prior-year financial statements to conform to the current-year presentation. We have updated our consolidated balance sheet at December 31, 2023, to disaggregate the following line items from their previous presentation to conform to our current-year presentation: “income tax receivable” from “other current assets” and “pension and other postemployment benefits” from “other assets.” We have also updated our consolidated balance sheet at December 31, 2023, to include “employee benefit obligations” within “other deferred credits.”
Recently Issued Accounting Standards Update - In November 2024, the FASB issued ASU-2024-03, “Disaggregation of Income Statement Expenses (Subtopic 220-40).” The amendments in this standard address requests from investors for more detailed information about the types of expenses commonly presented in income statements and will require a footnote disclosure to disaggregate, in a tabular presentation, each relevant expense category on the face of the income statement that includes any of the following natural expenses: purchases of inventory, employee compensation, depreciation, intangible asset amortization, and depreciation, depletion, and amortization recognized as part of oil- and gas-producing activities or other types of depletion expenses. The amendments in this update are effective for annual periods beginning after December 15, 2026, and
interim periods within annual periods beginning after December 15, 2027. We are currently assessing the timing and impacts of adopting this standard.

In December 2023, the FASB issued ASU 2023-09, “Income Taxes (Topic 740): Improvements to Income Tax Disclosures,” which is intended to enhance annual income tax disclosures to address investor requests for more information about the tax risks and opportunities present in an entity’s operations. The amendments in this standard require disclosure of additional information in specified categories with respect to the reconciliation of the effective tax rate to the statutory rate (the rate reconciliation) for federal, state, and foreign income taxes. They also require greater detail about individual reconciling items in the rate reconciliation to the extent the impact of those items exceeds a specified threshold. In addition to new disclosures associated with the rate reconciliation, the amendments in this update require information pertaining to taxes paid (net of refunds received) to be disaggregated for federal, state, and foreign taxes and further disaggregated for specific jurisdictions to the extent the related amounts exceed a quantitative threshold. The amendments in this update are effective for annual periods beginning after December 15, 2024. We adopted this guidance for 2024 — earlier than the effective date. Our adoption did not result in a material impact to our consolidated financial statements. See Note 12 for additional information regarding income taxes.

In November 2023, the FASB issued ASU 2023-07, “Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures,” which is intended to improve annual and interim reportable segment disclosure requirements, primarily through enhanced disclosures about significant segment expenses. The amendments in this standard enhance interim disclosure requirements, clarify circumstances in which an entity can disclose multiple segment measures of profit or loss, provide new segment disclosure requirements for entities with a single reportable segment, and contain other disclosure requirements. The amendments in this update are effective for annual periods beginning after December 15, 2023, and interim periods within annual periods beginning after December 15, 2024. We adopted this guidance as of the effective date. Our adoption did not result in a material impact to our consolidated financial statements and disclosures.
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REVENUE (Notes)
 12 Months Ended
Dec. 31, 2024
Revenue from Contract with Customer REVENUE
The following table sets forth our revenues disaggregated by source for the periods indicated:

Year Ended December 31,
202420232022
(Thousands of dollars)
Natural gas sales to customers$1,841,400 $2,141,908 $2,410,048 
Transportation revenues137,111 132,945 125,951 
Securitization customer charges (Note 17)
44,390 48,677 5,769 
Miscellaneous revenues22,971 22,791 19,850 
Total revenues from contracts with customers2,045,872 2,346,321 2,561,618
Other revenues - natural gas sales related24,296 12,764 3,403 
Other revenues 13,390 12,905 12,984 
Total other revenues37,686 25,669 16,387 
Total revenues$2,083,558 $2,371,990 $2,578,005 
Accrued unbilled natural gas sales revenues at December 31, 2024 and December 31, 2023, were $212.0 million and $191.4 million, respectively, and are included in accounts receivable on our consolidated balance sheets.
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REGULATORY ASSETS AND LIABILITIES (Notes)
 12 Months Ended
Dec. 31, 2024
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]  
Schedule of Regulatory Assets and Liabilities REGULATORY ASSETS AND LIABILITIES
The tables below present a summary of regulatory assets and liabilities, net of amortization, for the periods indicated:

December 31, 2024
Recovery PeriodCurrentNoncurrentTotal
(Thousands of dollars)
Winter weather event costs(a)$9,051 $15,938 $24,989 
Under-recovered purchased-gas costs1 year43,819 — 43,819 
Pension and postemployment benefit costs, net
See Note 11
1,358 224,837 226,195 
Reacquired debt costs4 years723 1,989 2,712 
MGP remediation costs15 years1,000 30,067 31,067 
Ad-valorem tax1 year14,066 — 14,066 
WNA1 year26,684 — 26,684 
Customer credit deferrals1 year255 3,639 3,894 
Other, net1 to 20 years4,254 1,536 5,790 
Total regulatory assets101,210 278,006 379,216 
Income tax rate changes(a)— (467,563)(467,563)
Over-recovered purchased-gas costs1 year(22,525)— (22,525)
Total regulatory liabilities(22,525)(467,563)(490,088)
Net regulatory assets and liabilities$78,685 $(189,557)$(110,872)
(a) Recovery period varies by jurisdiction. See discussion below for additional information regarding our regulatory assets related to winter weather event costs and regulatory liabilities related to income tax rate changes.

December 31, 2023
Recovery PeriodCurrentNoncurrentTotal
(Thousands of dollars)
Winter weather event costs(a)$22,633 $21,495 $44,128 
Under-recovered purchased-gas costs1 year10,391 — 10,391 
Pension and postemployment benefit costs
See Note 11
6,379 228,092 234,471 
Reacquired debt costs6 years723 2,712 3,435 
MGP remediation costs15 years98 31,893 31,991 
Ad-valorem tax1 year14,533 — 14,533 
WNA1 year11,404 — 11,404 
Customer credit deferrals1 year6,184 — 6,184 
Other1 to 18 years2,963 3,714 6,677 
Total regulatory assets75,308 287,906 363,214 
Income tax rate changes(a)— (500,478)(500,478)
Over-recovered purchased-gas costs1 year(66,901)— (66,901)
Total regulatory liabilities(66,901)(500,478)(567,379)
Net regulatory assets and liabilities$8,407 $(212,572)$(204,165)
(a) Recovery period varies by jurisdiction. See discussion below for additional information regarding our regulatory assets related to winter weather event costs and regulatory liabilities related to income tax rate changes.

Regulatory assets in our consolidated balance sheets, as authorized by various regulatory authorities, are probable of recovery. Base rates and certain riders are designed to provide a recovery of costs during the period such rates are in effect, but do not generally provide for a return on investment for amounts we have deferred as regulatory assets. All of our regulatory assets are subject to review by the respective regulatory authorities during future regulatory proceedings.
Other regulatory assets and liabilities - Purchased-gas costs represent the natural gas costs that have been over- or under-recovered from customers through the purchased-gas cost adjustment mechanisms, and includes natural gas utilized in our operations and premiums paid and any cash settlements received from our purchased natural gas call options.

The OCC, KCC and regulatory authorities in Texas have approved the recovery of pension costs and other postemployment benefits costs through rates for Oklahoma Natural Gas, Kansas Gas Service and Texas Gas Service, respectively. The costs recovered through rates are based on the net periodic benefit cost for defined benefit pension and other postemployment costs.
Differences, if any, between the net periodic benefit cost (credit), net of deferrals, and the amount recovered through rates are reflected in earnings. We historically have recovered defined benefit pension and other postemployment benefit costs through rates. We believe it is probable that regulators will continue to include the net periodic pension and other postemployment benefit costs in our cost of service.

We amortize reacquired debt costs in accordance with the accounting guidelines prescribed by the OCC and the KCC.

See Note 15 for additional information regarding our regulatory assets for MGP remediation costs.

Ad-valorem tax represents the difference in Kansas Gas Service’s taxes incurred each year above or below the amount approved in base rates. This difference is deferred as a regulatory asset or liability for a 12-month period. Kansas Gas Service then applies an adjustment to customers’ bills to refund the over-collected revenue or bill the under-collected revenue over the subsequent 12 months.

Weather normalization represents revenue over- or under-recovered through the WNA rider in Kansas. This amount is deferred as a regulatory asset or liability for a 12-month period. Kansas Gas Service then applies an adjustment to customers’ bills for 12 months to refund the over-collected revenue or bill the under-collected revenue.

The customer credit deferrals and the noncurrent regulatory liability for income tax rate changes represents deferral of the effects of enacted federal and state income tax rate changes on our ADIT and the effects of these changes on our rates. See Note 12 for additional information regarding the impact of income tax rate changes.
Recovery through rates resulted in amortization of regulatory assets, net, of approximately $14.4 million, $14.7 million and $9.4 million for the years ended December 31, 2024, 2023 and 2022, respectively.
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CREDIT FACILITIES (Notes)
 12 Months Ended
Dec. 31, 2024
Line of Credit Facility [Abstract]  
Short-term Debt [Text Block]
4.    CREDIT FACILITY AND SHORT-TERM DEBT

In June 2024, we entered into an agreement that increased the capacity of the ONE Gas Credit Agreement to $1.275 billion from $1.2 billion with commitments from existing lenders and the addition of a new lender.

In October 2024, we entered into an agreement that increased the capacity of the ONE Gas Credit Agreement to $1.35 billion from $1.275 billion with commitments from existing lenders and the addition of a new lender. Other than the increased commitments and the addition of a new lender, all other terms and conditions of the ONE Gas Credit Agreement remain in full force and effect, including the maturity date of March 16, 2028.

The ONE Gas Credit Agreement provides for a $1.35 billion revolving unsecured credit facility and includes a $20 million letter of credit subfacility and a $60 million swingline subfacility. We can request an increase in commitments of up to an additional $150 million upon satisfaction of customary conditions, including receipt of commitments from either new lenders or increased commitments from existing lenders. The ONE Gas Credit Agreement is available to provide liquidity for working capital, capital expenditures, acquisitions and mergers, the issuance of letters of credit and for other general corporate purposes.

The ONE Gas Credit Agreement contains certain financial, operational and legal covenants. Among other things, these covenants include maintaining ONE Gas’ total debt-to-capital ratio of no more than 70 percent at the end of any calendar quarter. At December 31, 2024, our total debt-to-capital ratio was 51.8 percent and we were in compliance with all covenants under the ONE Gas Credit Agreement. Excluding the debt of KGSS-I, which is non-recourse to us, our total debt-to-capital ratio was 49.5 percent. We may reduce the unutilized portion of the ONE Gas Credit Agreement in whole or in part without premium or penalty. The ONE Gas Credit Agreement contains customary events of default. Upon the occurrence of certain events of default, our obligations under the ONE Gas Credit Agreement may be accelerated and the commitments may be terminated.

At December 31, 2024, we had $1.35 million in letters of credit issued and no borrowings under the ONE Gas Credit Agreement, with approximately $1.349 billion of remaining credit, which is available to repay our commercial paper borrowings.

In July 2024, we increased the capacity of our commercial paper program to $1.275 billion from $1.2 billion.

In October 2024, we increased the capacity of our commercial paper program to $1.35 billion from $1.275 billion. Under our commercial paper program, we may issue unsecured commercial paper to fund short-term borrowing needs. The maturities of the commercial paper vary but may not exceed 270 days from the date of issue. Commercial paper is generally sold at par less a
discount representing an interest factor. At December 31, 2024 and December 31, 2023, we had $914.6 million and $88.5 million of commercial paper outstanding with a weighted-average interest rate of 4.77 percent and 5.60 percent, respectively.
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LONG-TERM DEBT (Notes)
 12 Months Ended
Dec. 31, 2024
Long-Term Debt, Unclassified [Abstract]  
Long-term Debt [Text Block] LONG-TERM DEBT
The table below presents a summary of our long-term debt outstanding for the periods indicated:

December 31,
Interest Rate
20242023
(Thousands of dollars)
Senior Notes due:
February 20243.610%$— $300,000 
March 20241.100%— 473,000 
April 20295.100%550,000 300,000 
May 20302.000%300,000 300,000 
September 20324.250%300,000 300,000 
February 20444.658%600,000 600,000 
November 20484.500%400,000 400,000 
Total Senior Notes2,150,000 2,673,000 
KGSS-I Securitized Utility Tariff Bonds5.486%287,345 315,284 
Unamortized discounts, net of premiums, on long-term debt(3,624)(7,615)
Debt issuance costs (a)(20,691)(21,092)
Other8.000%1,226 1,238 
Total long-term debt, net2,414,256 2,960,815 
Less: current maturities of KGSS-I securitized utility tariff bonds, net28,956 27,430 
Less: current maturities of other long-term debt, net14 772,984 
Noncurrent portion of long-term debt, net$2,385,286 $2,160,401 
(a) Includes issuance costs and discounts for the KGSS-I Securitized Utility Tariff Bonds of $4.8 million and $5.3 million, at December 31, 2024 and December 31, 2023 respectively.
Senior Notes - The indenture governing our Senior Notes includes an event of default upon the acceleration of other indebtedness of $100 million or more. Such events of default would entitle the trustee or the holders of 25 percent in aggregate principal amount of the outstanding Senior Notes to declare those Senior Notes immediately due and payable in full.

Depending on the series, we may redeem our Senior Notes at par, plus accrued and unpaid interest to the redemption date, starting one month, three months or six months before their maturity dates. Prior to these dates, we may redeem these Senior Notes, in whole or in part, at a redemption price equal to the principal amount, plus accrued and unpaid interest and a make-whole premium. The redemption price will never be less than 100 percent of the principal amount of the respective Senior Note plus accrued and unpaid interest to the redemption date. Senior Notes are senior unsecured obligations, ranking equally in right of payment with all of our existing and future unsecured senior indebtedness.

In December 2023, we issued $300 million of 5.10 percent senior notes due April 2029. The proceeds from the issuance were used to repay amounts outstanding under our commercial paper program and for general corporate purposes.

We repaid our $300 million of 3.61 percent senior notes due February 2024 and our $473 million of 1.10 percent senior notes due March 2024 upon maturity with commercial paper.

In August 2024, we reopened our outstanding 5.10 percent senior notes due 2029 and issued an additional $250 million. After the completion of this offering, the aggregate principal amount of the outstanding 5.10 percent senior notes due 2029 is $550 million.
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Leases
 12 Months Ended
Dec. 31, 2024
Leases [Abstract]  
Lessee, Operating Leases LEASES
We have operating leases for office facilities, gas storage facilities, IT equipment and right-of-way contracts. Our leases have remaining lease terms of less than one year to five years, some of which include options to extend the leases for up to 10 years, and some of which include options to terminate the leases within specified time frames. We have not entered into any finance leases.
Our right-of-use asset is $17.5 million and $21.0 million as of December 31, 2024 and 2023, respectively, and is reported within other assets in our consolidated balance sheets. Operating lease liabilities are reported within our accounts payable and other liabilities in our consolidated balance sheets. Total operating lease cost including immaterial amounts attributable to short-term operating leases was $7.7 million, $7.7 million, and $7.8 million in 2024, 2023 and 2022, respectively.
In 2024, we reassessed certain operating leases for office facilities and IT equipment which were extended or modified, resulting in an increase of $2.7 million in our right-of-use asset and operating lease liability.

Year Ended
December 31,
Other information related to operating leases202420232022
(Millions of dollars)
Weighted-average remaining lease term4 years4 years5 years
Weighted-average discount rate4.37 %4.28 %4.04 %
Supplemental cash flows information
Lease payments$(7.9)$(8.3)$(8.2)
Right-of-use assets obtained in exchange for lease obligations$2.7 $3.9 $0.3 

December 31,
Future minimum lease payments under non-cancellable operating leases2024
(Millions of dollars)
2025$5.9 
20264.3 
20273.3 
20283.0 
20291.5 
Thereafter— 
Total future minimum lease payments$18.0 
Imputed interest(1.4)
Total operating lease liability$16.6 
Consolidated balance sheets as of December 31, 2024
Current operating lease liability$5.2 
Long-term operating lease liability11.4 
Total operating lease liability$16.6 
v3.25.0.1
EQUITY (Notes)
 12 Months Ended
Dec. 31, 2024
Class of Stock [Line Items]  
Stockholders' Equity Note Disclosure [Text Block] EQUITY
Preferred Stock - At December 31, 2024, we had 50 million, $0.01 par value, authorized shares of preferred stock available. We have not issued or established any classes or series of shares of preferred stock.

Common Stock - At December 31, 2024, we had approximately 190.1 million shares of authorized common stock available for issuance.

Equity Issuances - On December 27, 2024, we settled under forward contracts 3,160,465 shares (926,465 shares from forwards related to an at-the-market equity distribution agreement and 2,234,000 from forwards related to underwriting agreements) of our common stock for net proceeds of $245.7 million ($75.2 million from forwards related to an at-the market equity distribution agreement and $170.5 million from forwards related to underwriting agreements).
In December 2024, we amended the two forward sale agreements we entered into in September 2023 to extend the maturity date of 223,000 and 180,000 shares of our common stock, to December 31, 2025 from December 31, 2024. The amended forward sale agreements provide for settlement on a date, or dates, to be specified at our discretion but which will occur no later than December 31, 2025.
In February 2023, we entered into an at-the-market equity distribution agreement under which we may issue and sell shares of our common stock with an aggregate offering price up to $300 million. This at-the-market equity program replaced our previous at-the-market equity program, which began in February 2020, and expired in February 2023. Sales of common stock are made by means of ordinary brokers’ transactions on the NYSE, in block transactions or as otherwise agreed to between us and the sales agent. We are under no obligation to offer and sell common stock under the program. At December 31, 2024, we had $225.5 million of equity available for issuance under the program.

The following table summarizes all of our outstanding forward sale agreements at December 31, 2024:

MaturityOriginal SharesRemaining SharesForward PriceNet Proceeds Available
(Shares)(Shares)(Per share)(Thousands of dollars)
December 31, 20251,200,000 223,000 $74.65 $16,647 
December 31, 2025180,000 180,000 74.60 13,428 
Total forward sale agreements1,380,000 403,000 $74.63 $30,075 
Dividends Declared - For the years ended December 31, 2024 and 2023, we declared and paid dividends of $2.64 per share ($0.66 per share quarterly) and $2.60 per share ($0.65 per share quarterly), respectively. In January 2025, we declared a dividend of $0.67 per share ($2.68 per share on an annualized basis) for shareholders of record as of February 21, 2025, payable on March 7, 2025.
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ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Notes)
 12 Months Ended
Dec. 31, 2024
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]  
Comprehensive Income (Loss) Note ACCUMULATED OTHER COMPREHENSIVE LOSS
The following table sets forth the balance in accumulated other comprehensive loss for the periods indicated:

Accumulated Other Comprehensive Loss
(Thousands of dollars)
January 1, 2023$(704)
Pension plan obligation
Other comprehensive income (loss) before reclassification, net of tax of $140
(477)
Amounts reclassified from accumulated other comprehensive loss, net of tax of $—
(1)
Other comprehensive income (loss)(478)
December 31, 2023(1,182)
Pension plan obligation
Other comprehensive income (loss) before reclassification, net of tax of $(281)
961 
Amounts reclassified from accumulated other comprehensive loss, net of tax of $—
(1)
Available-for-sale securities
Other comprehensive income (loss) before reclassification, net of tax of $(24)
94 
Amounts reclassified from accumulated other comprehensive loss, net of tax of $(1)
2 
Other comprehensive income (loss)1,056 
December 31, 2024$(126)
The following table sets forth the effect of reclassifications from accumulated other comprehensive loss in our consolidated statements of income for the periods indicated:

Year EndedAffected Line Item in the
Details About Accumulated Other December 31,Consolidated Statements
Comprehensive Loss Components202420232022of Income
(Thousands of dollars)
Pension and other postemployment benefit plan obligations (a)
Amortization of net gain (loss)$(5,770)$(1,960)$(17,010)
Amortization of unrecognized prior service credit (cost)(372)(525)(289)
(6,142)(2,485)(17,299)
Regulatory adjustments (b)6,143 2,486 17,141 
Amounts reclassified from accumulated other comprehensive loss1 1 (158)Other income (expense), net
Available-for-sale securities
Amounts reclassified from accumulated other comprehensive loss(3)— — Other income (expense), net
Total available-for-sale securities(3)— — 
Total reclassifications before tax(2)1 (158)Income before income taxes
Tax effect of reclassifications1 — 36 Income tax expense
Net reclassifications for the period$(1)$1 $(122)Net income
(a) These components of accumulated other comprehensive loss are included in the computation of net periodic benefit credit. See Note 11 for additional detail of our net periodic benefit credit.
(b) Regulatory adjustments represent pension and other postemployment benefit credits or costs expected to be recovered through rates and are deferred as part of our regulatory assets. See Note 3 for additional disclosures of regulatory assets and liabilities.
v3.25.0.1
EARNINGS PER SHARE (Notes)
 12 Months Ended
Dec. 31, 2024
EARNINGS PER SHARE [Line Items]  
Earnings Per Share [Text Block] EARNINGS PER SHARE
Basic EPS is calculated by dividing net income by the daily weighted-average number of common shares outstanding during the periods presented, which includes fully vested stock awards that have not yet been issued as common stock. Diluted EPS is based on shares outstanding for the calculation of basic EPS, plus unvested stock awards granted under our compensation plans and equity forward sale agreements, but only to the extent these instruments dilute earnings per share.

The following tables set forth the computation of basic and diluted EPS from continuing operations for the periods indicated:

Year Ended December 31, 2024
IncomeSharesPer Share
Amount
(Thousands, except per share amounts)
Basic EPS Calculation
Net income available for common stock
$222,850 56,826 $3.92 
Diluted EPS Calculation
Effect of dilutive securities— 207 
Net income available for common stock and common stock equivalents$222,850 57,033 $3.91 
Year Ended December 31, 2023
IncomeSharesPer Share
Amount
(Thousands, except per share amounts)
Basic EPS Calculation
Net income available for common stock
$231,232 55,600 $4.16 
Diluted EPS Calculation
Effect of dilutive securities— 260 
Net income available for common stock and common stock equivalents$231,232 55,860 $4.14 
Year Ended December 31, 2022
IncomeSharesPer Share
Amount
(Thousands, except per share amounts)
Basic EPS Calculation
Net income available for common stock
$221,742 54,207 $4.09 
Diluted EPS Calculation
Effect of dilutive securities— 131 
Net income available for common stock and common stock equivalents$221,742 54,338 $4.08 
v3.25.0.1
Compensation Related Costs, Share Based Payments
 12 Months Ended
Dec. 31, 2024
Share-Based Payment Arrangement [Abstract]  
Share-Based Payment Arrangement SHARE-BASED PAYMENTS
The ECP provides for the granting of stock-based compensation, including incentive stock options, nonstatutory stock options, stock bonus awards, restricted stock awards, restricted stock unit awards, performance stock awards and performance unit awards to eligible employees and the granting of stock awards to non-employee directors. At December 31, 2024, we have 4.3 million shares of common stock reserved for issuance under the ECP. At December 31, 2024, we had approximately 1.7 million shares available for issuance under the ECP, which reflect shares issued and estimated shares expected to be issued upon vesting of outstanding awards granted under the plan, less forfeitures. The plan allows for the deferral of awards granted in stock or cash, in accordance with the Code section 409A requirements.

Compensation expense for our ECP share-based payment plans was $8.8 million, net of tax benefits of $2.9 million, for 2024, $7.8 million, net of tax benefits of $2.6 million, for 2023, and $6.8 million, net of tax benefits of $2.3 million, for 2022.

Restricted Stock Unit Awards - We have granted restricted stock unit awards to key employees that vest over a service period of generally three years and entitle the grantee to receive shares of our common stock. Restricted stock unit awards granted accrue dividend equivalents in the form of additional restricted stock units prior to vesting. Restricted stock unit awards are measured at fair value as if they were vested and issued on the grant date and adjusted for estimated forfeitures. Compensation
expense is recognized on a straight-line basis over the vesting period of the award. A forfeiture rate of 3 percent per year based on historical forfeitures under our share-based payment plans is used.

Performance Stock Unit Awards - We have granted performance stock unit awards to key employees. The shares of common stock underlying the performance stock units vest at the expiration of a service period of generally three years if certain performance criteria are met by us as determined by the Executive Compensation Committee of the Board of Directors. Upon vesting, a holder of performance stock units is entitled to receive a number of shares of common stock equal to a percentage (0 percent to 200 percent) of the performance stock units granted, based on our total shareholder return over the vesting period, compared with the total shareholder return of a peer group of other utilities over the same period.

If paid, the outstanding performance stock unit awards entitle the grantee to receive shares of our common stock. The outstanding performance stock unit awards are equity awards with a market-based condition, which results in the compensation expense for these awards being recognized on a straight-line basis over the requisite service period, provided that the requisite service period is fulfilled, regardless of when, if ever, the market condition is satisfied. The performance stock unit awards granted accrue dividend equivalents in the form of additional performance stock units prior to vesting. The fair value of these performance stock units was estimated on the grant date based on a Monte Carlo model. The compensation expense on these awards will only be adjusted for forfeitures. A forfeiture rate of 3 percent per year based on historical forfeitures under our share-based payment plans is used.

Restricted Stock Unit Award Activity

Total unrecognized compensation expense related to the nonvested restricted stock unit awards was $4.2 million and $4.0 million as of December 31, 2024 and 2023, respectively, which is expected to be recognized over a weighted-average period of 1.7 years. The following tables set forth activity and various statistics for restricted stock unit awards outstanding under the respective plans for the period indicated:

Number of
Units		Weighted-
Average Grant Date Fair Value
Nonvested at December 31, 2023
126,948 $77.50 
Granted67,432 60.74 
Vested(41,168)72.46 
Forfeited(4,175)71.40 
Nonvested at December 31, 2024
149,037 $68.79 

 202420232022
Weighted-average grant date fair value (per share)
$60.74 $81.79 $76.96 
Fair value of shares granted (thousands of dollars)
$4,096 $3,995 $4,342 

For the years ended December 31, 2024, 2023 and 2022, the fair value of restricted stock vested was $3.2 million, $2.8 million, and $2.9 million, respectively.

Performance Stock Unit Award Activity

Total unrecognized compensation expenses related to the nonvested performance stock unit awards was $10.0 million and $9.7 million as of December 31, 2024 and 2023, respectively, which is expected to be recognized over a weighted-average period of 1.7 years. The following tables set forth activity and various statistics related to our performance stock unit awards and the assumptions used by us in the valuations of the 2024, 2023 and 2022 grants at the grant date:

Number of
Units		Weighted-
Average Grant Date Fair Value
Nonvested at December 31, 2023
247,326 $95.23 
Granted139,727 67.83 
Vested— — 
Forfeited(81,568)82.85 
Nonvested at December 31, 2024
305,485 $86.00 
202420232022
Volatility (a)26.63% 29.20%34.00%
Dividend yield4.35%3.18%3.22%
Risk-free interest rate (b)4.46%4.37%1.65%
(a) - Volatility based on historical volatility over three years using daily stock price observations of our peer utilities.
(b) - Using 3-year treasury rate.

202420232022
Weighted-average grant date fair value (per share)
$67.83 $105.74 $95.80 
Fair value of shares granted (thousands of dollars)
$9,478 $10,095 $8,360 

For the year ended December 31, 2024, there was no vested performance stock. For the years ended December 31, 2023 and 2022, the fair value of performance stock vested was $3.7 million and $5.2 million, respectively.

Employee Stock Purchase Plan

We have reserved a total of 1.25 million shares of common stock for issuance under our ESPP. Employees can choose to have up to 10 percent of their annual base pay withheld to purchase our common stock, subject to terms and limitations of the plan. The purchase price of the stock is 85 percent of the lower of the average market price of our common stock on the grant date or exercise date. Approximately 44 percent, 45 percent and 42 percent of employees participated in the plan in 2024, 2023 and 2022, respectively. For the years ended December 31, 2024, 2023 and 2022, employees purchased 122,906, 108,875, and 86,657 shares, respectively, at an average price of $53.98, $58.98 and $65.21, respectively.

Compensation expense related to our ESPP, before taxes, was $1.5 million, $1.2 million and $1.1 million for the years ended December 31, 2024, 2023 and 2022, respectively.
v3.25.0.1
EMPLOYEE BENEFIT PLANS (Notes)
 12 Months Ended
Dec. 31, 2024
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]  
Employee Benefit Plans (Notes) EMPLOYEE BENEFIT PLANS
Defined Benefit Pension and Other Postemployment Benefit Plans

Defined Benefit Pension Plans - We have a defined benefit pension plan and a supplemental executive retirement plan for certain eligible employees, both of which are closed to new participants. Certain employees of the Texas Gas Service division are entitled to benefits under a frozen cash-balance pension plan. We fund our defined benefit pension costs at a level needed to maintain or exceed the minimum funding levels required by the Employee Retirement Income Security Act of 1974, as amended, and the Pension Protection Act of 2006.

Other Postemployment Benefit Plans - We sponsor health and welfare plans that provide postemployment medical and life insurance benefits to certain eligible employees who retire with at least five years of service. The postemployment medical plan is contributory based on hire date, age and years of service, with retiree contributions adjusted periodically, and contains other cost-sharing features such as deductibles and coinsurance.

Actuarial Assumptions - The following table sets forth the weighted-average assumptions used to determine benefit obligations for pension and postemployment benefits for the periods indicated:

December 31,
 20242023
Discount rate - pension plans5.70%5.30%
Discount rate - other postemployment plans5.75%5.40%
Compensation increase rate
 3.50% - 4.30%
3.50% - 4.30%
The following table sets forth the weighted-average assumptions used by us to determine the periodic benefit costs for pension and postemployment benefits for the periods indicated:

Year Ended December 31,
 202420232022
Discount rate - pension plans5.30%5.60%
3.05%/4.55% (a)
Discount rate - other postemployment plans5.40%5.70%3.00%
Expected long-term return on plan assets - pension plans6.70%6.75%6.40%
Expected long-term return on plan assets - other postemployment plans5.20%5.55%5.85%
Compensation increase rate
3.50% - 4.30%
3.60% - 5.00%
3.10% - 5.00%
(a) Pension plans were remeasured as of April 30, 2022.

We determine our discount rates annually. We estimate our discount rate based upon a comparison of the expected cash flows associated with our future payments under our defined benefit pension and other postemployment obligations to a hypothetical bond portfolio created using high-quality bonds that closely match expected cash flows. Bond portfolios are developed by selecting a bond for each of the next 60 years based on the maturity dates of the bonds. Bonds selected to be included in the portfolios are only those rated by Moody’s as AA- or better and exclude callable bonds, bonds with less than a minimum issue size, yield outliers and other filtering criteria to remove unsuitable bonds.

We determine our overall expected long-term rate of return on plan assets based on our review of historical returns and economic growth models. We update our assumed mortality rates to incorporate new tables issued by the Society of Actuaries as needed.

Regulatory Treatment - The OCC, KCC and regulatory authorities in Texas have approved the recovery of pension and other postemployment benefits costs through rates for Oklahoma Natural Gas, Kansas Gas Service and Texas Gas Service, respectively. The costs recovered through rates are based on current funding requirements and the net periodic benefit cost for defined benefit pension and other postemployment costs. Differences, if any, between the net periodic benefit cost (credit), net of deferrals, and the amount recovered through rates are reflected in earnings.

We historically have recovered defined benefit pension and other postemployment benefit costs (credit) through rates. We believe it is probable that regulators will continue to include the net periodic pension and other postemployment benefit costs (credit) in our cost of service.

We capitalize all eligible service cost and non-service credit components pursuant to the accounting requirements of ASC Topic 980 (Regulated Operations) for rate-regulated entities, as these components are authorized by our regulators to be included in capitalized costs. Noncurrent regulatory liabilities in our consolidated balance sheets reflect the capitalized non-service credit components of $6.7 million and $2.2 million as of December 31, 2024 and 2023, respectively. See Note 3 for additional information.
Obligations and Funded Status - The following table sets forth our defined benefit pension and other postemployment benefit plans, benefit obligations and fair value of plan assets for the periods indicated:

Pension BenefitsOther Postemployment Benefits
December 31, December 31,
2024202320242023
Changes in Benefit Obligation(Thousands of dollars)
Benefit obligation, beginning of period$803,605 $784,633 $158,535 $168,342 
Service cost6,204 7,242 610 730 
Interest cost41,123 42,428 8,179 9,154 
Plan participants’ contributions— — 2,631 2,823 
Actuarial loss (gain)
(27,026)23,015 (3,267)(5,551)
Benefits paid
(54,099)(53,713)(15,704)(16,963)
Settlements(38,690)— — — 
Benefit obligation, end of period$731,117 $803,605 $150,984 $158,535 
Change in Plan Assets
Fair value of plan assets, beginning of period$795,381 $768,961 $181,608 $181,877 
Actual return on plan assets
22,322 78,827 8,404 11,325 
Employer contributions1,559 1,306 — 2,546 
Plan participants’ contributions— — 2,631 2,823 
Benefits paid
(54,099)(53,713)(13,154)(16,963)
Settlements(39,762)— — — 
Fair value of assets, end of period725,401 795,381 179,489 181,608 
Benefit asset (obligation), net
$(5,716)$(8,224)$28,505 $23,073 
Pension and other postemployment benefits$14,377 $13,409 $28,505 $23,073 
Current liabilities(1,409)(1,368)— — 
Noncurrent liabilities(18,684)(20,265)— — 
Benefit asset (obligation), net$(5,716)$(8,224)$28,505 $23,073 

The accumulated benefit obligation for our defined benefit pension plans was $703.4 million and $772.1 million at December 31, 2024 and 2023, respectively.

For the years ended December 31, 2024 and 2023, the pension benefit obligations experienced actuarial gains and losses of $27.0 million and $23.0 million, respectively, primarily due to the impact of increases in the discount rates used to calculate the benefit obligations.

In 2025, our contributions are expected to be $9.8 million to our defined benefit pension plans, and no contributions are expected to be made to our other postemployment benefit plans. In October 2024, we purchased group annuity contracts and transferred approximately $39 million of the assets and liabilities related to certain participants in our deferred benefit pension plan to a third-party insurance company.
The following tables set forth the components of net periodic benefit cost for our pension and other postemployment benefit plans for the periods indicated:

Pension Benefits
Year Ended December 31,
202420232022
(Thousands of dollars)
Components of net periodic benefit cost (credit)
 
Service cost$6,204 $7,242 $10,369 
Interest cost (a)
41,123 42,428 36,150 
Expected return on assets (a)
(59,027)(59,518)(58,528)
Amortization of unrecognized prior service cost (a)
372 372 248 
Amortization of net loss (a)
5,786 2,008 16,793 
Net periodic benefit cost (credit)
$(5,542)$(7,468)$5,032 
(a) These amounts, net of any amounts capitalized as a regulatory asset, have been recognized as other (income) expense, net in the consolidated statement of income. See Note 13 for additional detail.

Other Postemployment Benefits
Year Ended December 31,
202420232022
(Thousands of dollars)
Components of net periodic benefit cost (credit)
Service cost$610 $730 $1,274 
Interest cost (a)
8,179 9,154 6,448 
Expected return on assets (a)
(9,134)(9,728)(13,181)
Amortization of unrecognized prior service cost (credit) (a)
— 153 41 
Amortization of net loss (gain) (a)
(16)(48)217 
Net periodic benefit cost (credit)
$(361)$261 $(5,201)
(a) These amounts, net of any amounts capitalized as a regulatory asset, have been recognized as other (income) expense, net in the consolidated statement of income. See Note 13 for additional detail.
We use a December 31 measurement date for our plans. On April 30, 2022, we amended our defined benefit pension plans to change the variable cost of living adjustment for eligible participants to a fixed rate. Accordingly, we remeasured our net benefit obligations as of April 30, 2022, resulting in an adjustment of approximately $7.2 million to our pension expense, net of capitalization and regulatory deferrals, for the year ended December 31, 2022.

Other Comprehensive Income (Loss) - The following table sets forth the amounts recognized in other comprehensive income (loss), net of regulatory deferrals, related to our defined benefit pension benefits for the period indicated:

Pension Benefits
Year Ended December 31,
202420232022
(Thousands of dollars)
Net gain (loss) arising during the period
$1,242 $(619)$7,369 
Amortization of net loss (gain)(1)1 159 
Deferred income taxes(281)140 (1,705)
   Total recognized in other comprehensive income (loss)
$960 $(478)$5,823 

Due to our regulatory deferrals, there were no amounts recognized in other comprehensive income (loss) related to our other postemployment benefits for the periods presented.
The tables below set forth the amounts in accumulated other comprehensive loss that had not yet been recognized as components of net periodic benefit credit for the periods indicated:

Pension Benefits
December 31,
20242023
(Thousands of dollars)
Prior service cost$(1,720)$(2,091)
Accumulated loss(251,952)(246,988)
Accumulated other comprehensive loss before regulatory asset(253,672)(249,079)
Regulatory asset for regulated entities253,517 247,684 
Accumulated other comprehensive loss after regulatory asset(155)(1,395)
Deferred income taxes(67)213 
Accumulated other comprehensive loss, net of tax$(222)$(1,182)

Other Postemployment Benefits
December 31,
20242023
(Thousands of dollars)
Prior service cost$— $— 
Accumulated gain (loss)1,065 (1,457)
Accumulated other comprehensive loss before regulatory asset1,065 (1,457)
Regulatory asset for regulated entities(1,065)1,457 
Accumulated other comprehensive loss after regulatory asset$— $— 

Health Care Cost Trend Rates - The following table sets forth the assumed health care cost-trend rates for the periods indicated:

20242023
Health care cost-trend rate assumed for next year7.00%6.00%
Rate to which the cost-trend rate is assumed to decline (the ultimate trend rate)4.50%4.50%
Year that the rate reaches the ultimate trend rate20352030

Plan Assets - Our investment strategy is to invest plan assets in accordance with sound investment practices that emphasize long-term fundamentals. The goal of this strategy is to maximize investment returns while managing risk in order to meet the plan’s current and projected financial obligations. To achieve this strategy, we have established a liability-driven investment strategy to change the allocations as the funded status of the defined benefit pension plan increases. The plan’s investments include a diverse blend of various domestic and international equities, investment-grade debt securities which mirror the cash flows of our liability, insurance contracts and alternative investments. The current target allocation for the assets of our defined benefit pension plan is as follows:

Investment-grade bonds70.0 %
U.S. large-cap equities13.0 %
Alternative investments7.0 %
Developed foreign equities5.0 %
Mid-cap equities3.0 %
Emerging markets equities1.0 %
Small-cap equities1.0 %
  Total100.0 %

As part of our risk management for the plans, minimums and maximums have been set for each of the asset classes listed above. All investment managers for the plan are subject to certain restrictions on the securities they purchase and, with the exception of indexing purposes, are prohibited from owning our stock.
The current target allocation for the assets of our other postemployment benefits plan is 90 percent fixed income securities and 10 percent equity securities.

The following tables set forth our pension and other postemployment benefits plan assets by fair value category as of the measurement date:

Pension Benefits
December 31, 2024
Asset CategoryLevel 1Level 2Level 3Total
(Thousands of dollars)
Investments:
Equity securities (a)$81,459 $— $— $81,459 
Government obligations— 213,572 — 213,572 
Corporate obligations (b)— 328,915 — 328,915 
Cash and money market funds (c)5,871 24,737 — 30,608 
Insurance contracts and group annuity contracts— — 11,177 11,177 
Other investments (d)— — 59,670 59,670 
  Total assets$87,330 $567,224 $70,847 $725,401 
(a) - This category represents securities of the various market sectors from diverse industries.
(b) - This category represents bonds from diverse industries.
(c) - This category primarily represents money market funds.
(d) - This category represents alternative investments such as hedge funds and other financial instruments.

Pension Benefits
December 31, 2023
Asset CategoryLevel 1Level 2Level 3Total
(Thousands of dollars)
Investments:
Equity securities (a)$88,477 $— $— $88,477 
Government obligations— 204,669 — 204,669 
Corporate obligations (b)— 366,482 — 366,482 
Cash and money market funds (c)5,300 28,977 — 34,277 
Insurance contracts and group annuity contracts— — 12,350 12,350 
Other investments (d)— — 89,126 89,126 
  Total assets$93,777 $600,128 $101,476 $795,381 
(a) - This category represents securities of the various market sectors from diverse industries.
(b) - This category represents bonds from diverse industries.
(c) - This category primarily represents money market funds.
(d) - This category represents alternative investments such as hedge funds and other financial instruments.

Other Postemployment Benefits
December 31, 2024
Asset CategoryLevel 1Level 2Level 3Total
(Thousands of dollars)
Investments:
Equity securities (a)$7,226 $— $— $7,226 
Government obligations— 41,982 — 41,982 
Corporate obligations (b)— 36,411 — 36,411 
Cash and money market funds (c)806 12,167 — 12,973 
Insurance contracts and group annuity contracts (d)— 80,897 — 80,897 
  Total assets$8,032 $171,457 $— $179,489 
(a) - This category represents securities of the various market sectors from diverse industries.
(b) - This category represents bonds from diverse industries.
(c) - This category primarily represents money market funds.
(d) - This category includes equity securities and bonds held in a captive insurance product.
Other Postemployment Benefits
December 31, 2023
Asset CategoryLevel 1Level 2Level 3Total
(Thousands of dollars)
Investments:
Equity securities (a)$7,031 $— $— $7,031 
Government obligations— 41,863 — 41,863 
Corporate obligations (b)— 38,615 — 38,615 
Cash and money market funds (c)751 13,245 — 13,996 
Insurance contracts and group annuity contracts (d)— 80,102 — 80,102 
  Total assets$7,782 $173,825 $— $181,607 
(a) - This category represents securities of the various market sectors from diverse industries.
(b) - This category represents bonds from diverse industries.
(c) - This category primarily represents money market funds.
(d) - This category includes equity securities and bonds held in a captive insurance product.

Insurance contracts and group annuity contracts include investments in the Immediate Participation Guarantee Fund (“IPG Fund”) with John Hancock and are valued at fair value. John Hancock invests the IPG Fund in its general fund portfolio. The contract value of the IPG Fund at the end of the year, which approximates fair value, is estimated. The difference between this estimated balance and the actual balance, as subsequently determined by John Hancock, is charged or credited to the net assets of the plans.

Certain investments that are categorized as money market funds in Level 2 and other investments in Level 3 represent alternative investments such as hedge funds and other financial instruments measured using the net asset value per share (or its equivalent) practical expedient.

The following tables set forth additional information regarding commitments and redemption limitations of these other investments at the periods indicated:

December 31, 2024
Fair ValueUnfunded CommitmentsRedemption FrequencyRedemption Notice Period
(in thousands)(in days)
Grosvenor Registered Multi Limited Partnership$29,642 $— quarterly65
K2 Institutional Investors II Limited Partnership$30,028 $— quarterly91

December 31, 2023
Fair ValueUnfunded CommitmentsRedemption FrequencyRedemption Notice Period
(in thousands)(in days)
Grosvenor Registered Multi Limited Partnership$40,872 $— quarterly65
K2 Institutional Investors II Limited Partnership$48,254 $— quarterly91
The following table sets forth the reconciliation of Level 3 fair value measurements of our pension plans for the periods indicated:

Pension Benefits
Insurance
Contracts		Other
Investments		Total
(Thousands of dollars)
January 1, 2023$14,480 $87,031 $101,511 
Unrealized gains— 2,095 2,095 
Unrealized losses(618)— (618)
Purchases1,562 — 1,562 
Settlements(3,074)— (3,074)
December 31, 2023$12,350 $89,126 $101,476 
Unrealized gains445 — 445 
Unrealized losses— (2,984)(2,984)
Expense(167)— (167)
Purchases— 1,408 1,408 
Sales— (27,880)(27,880)
Benefits paid(1,451)— (1,451)
December 31, 2024$11,177 $59,670 $70,847 

Pension and Other Postemployment Benefit Payments - Benefit payments for our defined benefit pension and other postemployment benefit plans for the year ended December 31, 2024 were $54.1 million and $15.7 million, respectively. The following table sets forth the pension benefits and other postemployment benefits payments expected to be paid in 2025-2034:

Pension
Benefits		Other Postemployment
Benefits
Benefits to be paid in:(Thousands of dollars)
2025$52,832 $14,127 
202653,298 13,734 
202753,470 13,431 
202854,189 13,069 
202954,094 12,745 
2030 through 2034271,532 58,985 

The expected benefits to be paid are based on the same assumptions used to measure our benefit obligations at December 31, 2024, and include estimated future employee service.

Other Employee Benefit Plans

401(k) Plan - We have a 401(k) plan which covers all eligible employees. Employee contributions are discretionary and we match 100 percent of each participant’s eligible contribution up to 6 percent of eligible compensation, subject to certain limits. Our contributions to the plan were $17.7 million, $16.7 million and $15.3 million in 2024, 2023 and 2022, respectively.

We plan to make a discretionary profit-sharing contribution to the 401(k) Plan each quarter equal to 1 percent of each participant’s eligible compensation during the quarter. Additional discretionary profit-sharing contributions may be made after the end of each year. Our profit-sharing contributions made to the plan were $10.9 million, $12.6 million and $10.9 million in 2024, 2023 and 2022, respectively.

Nonqualified Deferred Compensation Plan - We have a nonqualified deferred compensation plan with obligations of $18.9 million and $16.0 million at December 31, 2024 and 2023, respectively, which are reported within other deferred credits in our consolidated balance sheets. These obligations represent the amount owed to plan participants and are treated as if invested in specified investment options. A significant portion of the obligation is indirectly funded with key-person corporate-owned life insurance policies to offset costs associated with our nonqualified deferred compensation plan and the supplemental executive retirement plan. These corporate-owned life insurance policies are measured at cash surrender value of $41.5 million and $37.9 million at December 31, 2024 and 2023, respectively, and are reported within other assets in our consolidated balance sheets.
Gains (losses) on the corporate-owned life insurance policies are recognized in other income (expense), net within our consolidated statements of income; see Note 13 for additional detail of our other income (expense), net. Deferred compensation expense (income) associated with the nonqualified deferred compensation plan is recognized in operations and maintenance expense within our consolidated statements of income and was $2.4 million, $2.3 million, and $(2.3) million for the years ended December 31, 2024, 2023 and 2022, respectively.
v3.25.0.1
INCOME TAXES (Notes)
 12 Months Ended
Dec. 31, 2024
Income Tax Disclosure [Abstract]  
Income Tax Disclosure INCOME TAXES
The following table sets forth our provision for income taxes for the periods indicated:

Year Ended December 31,
202420232022
(Thousands of dollars)
Current income tax provision (benefit)
Federal$(68,660)$16,551 $61,745 
State(1,476)(829)6,815 
Total current income tax provision (benefit)(70,136)15,722 68,560 
Deferred income tax provision (benefit)
Federal110,717 21,905 (22,234)
State(4,195)2,868 200 
Total deferred income tax provision (benefit)106,522 24,773 (22,034)
Total provision for income taxes$36,386 $40,495 $46,526 

The following table is a reconciliation of our income tax provision for the periods indicated:

Year Ended December 31,
202420232022
(Thousands of dollars, except percentages)
Income before income taxes$259,236 $271,727 $268,268 
Federal statutory income tax rate21 %21 %21 %
Provision for federal income taxes54,439 21%57,063 21%56,335 21%
State income taxes, net of federal tax benefit4,333 2%3,834 1%7,016 3%
Tax effect of permanent differences2,018 1%1,860 1%1,369 1%
Tax effect of state income tax deduction(209)—%(443)—%(1,254)—%
Amortization of excess deferred federal income taxes(15,680)(6)%(20,565)(8)%(17,986)(7)%
Amortization of excess deferred state income taxes(10,004)(4)%(1,795)(1)%— —%
Tax (expense) benefit for employee share-based compensation1,063 —%418 —%350 —%
Other, net426 —%123 —%696 —%
Total provision for income taxes and effective income tax rate$36,386 14%$40,495 14%$46,526 18%

As of December 31, 2024, we have no uncertain tax positions. Changes in tax laws or tax rates are recognized in the financial reporting period that includes the enactment date. Oklahoma accounts for over 50 percent of state income taxes, net of federal tax benefits, and effect of state income taxes. In 2024, the IRS issued Revenue Procedure 2024-15, which allows for the deferral of income taxes on securitization bond proceeds received from a qualifying state financing entity. In 2022, Oklahoma Natural Gas received $1.3 billion in securitization bond proceeds and reported this amount as income on its federal income tax return for that year. Following the new revenue procedure, we amended our 2022 federal tax return to request a refund of $55.5 million, pending review and approval by the IRS. Additionally, we plan to file an amended Oklahoma corporate income tax return in the first quarter of 2025 to request a state refund of $1.5 million.

Income tax expense reflects credits for the amortization of the regulatory liability associated with EDIT, embedded in base rates, of $25.7 million and $22.4 million for the years ending December 31, 2024, and 2023, respectively.
The following table sets forth the tax effects of temporary differences that gave rise to significant portions of the deferred tax assets and liabilities for the periods indicated:

December 31,
20242023
(Thousands of dollars)
Deferred tax assets
Employee benefits and other accrued liabilities$— $— 
Regulatory adjustments for enacted tax rate changes100,718 107,948 
Net operating loss405,316 93,255 
Lease obligation basis3,669 4,500 
Purchased-gas cost adjustment— 5,232 
Other— — 
Total deferred tax assets509,703 210,935 
Deferred tax liabilities
Excess of tax over book depreciation930,680 822,619 
Winter weather event costs381,818 56,914 
Purchased-gas cost adjustment8,654 — 
Other regulatory assets and liabilities, net73,904 70,384 
Employee benefits and other accrued liabilities934 205 
Right-of-use asset basis3,866 4,662 
Other1,585 8,219 
Total deferred tax liabilities1,401,441 963,003 
Net deferred tax liabilities$891,738 $752,068 

At December 31, 2024 we had $378.9 million (tax effected) of federal net operating loss carryforwards and $26.4 million (tax effected) of state net operating loss carryforwards available to offset future taxable income.

We have filed our consolidated federal and state income tax returns for years 2021, 2022 and 2023. We are no longer subject to income tax examination for years prior to 2020.
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OTHER INCOME AND OTHER EXPENSE (Notes)
 12 Months Ended
Dec. 31, 2024
Other Income and Other Expense Disclosure [Text Block] OTHER INCOME AND OTHER EXPENSE
The following table sets forth the components of other income and other expense for the periods indicated:

Year Ended December 31,
202420232022
(Thousands of dollars)
Net periodic benefit credit other than service cost
$3,600 $4,017 $3,766 
Gain (loss) on investments associated with nonqualified deferred compensation plans
3,653 4,826 (7,197)
Other income (expense), net174 633 (752)
Total other income, net
$7,427 $9,476 $(4,183)
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Property, Plant, and Equipment
 12 Months Ended
Dec. 31, 2024
Property, Plant and Equipment [Abstract]  
Property, Plant and Equipment Disclosure PROPERTY, PLANT AND EQUIPMENT
The following table sets forth our property, plant and equipment by property type, for the periods indicated:

December 31,
20242023
(Thousands of dollars)
Natural gas distribution pipelines and related equipment$7,278,542 $6,716,074 
Natural gas transmission pipelines and related equipment736,229 713,505 
General plant and other942,677 907,946 
Construction work in process166,686 131,442 
Property, plant and equipment9,124,134 8,468,967 
Accumulated depreciation and amortization(2,478,261)(2,333,755)
Net property, plant and equipment$6,645,873 $6,135,212 

We compute depreciation expense by applying composite, straight-line rates of approximately 2.7 percent to 3.2 percent as approved by various regulatory authorities.

We recorded capitalized interest of $8.2 million, $5.7 million and $4.5 million for the years ended December 31, 2024, 2023 and 2022, respectively. We incurred liabilities for construction work in process and asset removal costs that had not been paid at December 31, 2024, 2023 and 2022 of $33.7 million, $36.2 million and $28.6 million, respectively. Such amounts are not included in capital expenditures or in the change of working capital items on our consolidated statements of cash flows.
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COMMITMENTS AND CONTINGENCIES (Notes)
 12 Months Ended
Dec. 31, 2024
Commitments and Contingencies [Line Items]  
COMMITMENTS AND CONTINGENCIES COMMITMENTS AND CONTINGENCIES
Leases - See Note 6 of the Notes to Consolidated Financial Statements in this Annual Report for discussion of operating leases.
Environmental Matters - We are subject to multiple laws and regulations regarding protection of the environment and natural and cultural resources, which affect many aspects of our present and future operations. Regulated activities include, but are not limited to, those involving air emissions, storm water and wastewater discharges, handling and disposal of solid and hazardous wastes, wetland preservation, plant and wildlife protection, hazardous materials use, storage and transportation, and pipeline and facility construction. These laws and regulations require us to obtain and/or comply with a wide variety of environmental clearances, registrations, licenses, permits and other approvals. Failure to comply with these laws, regulations, licenses and permits or the discovery of presently unknown environmental conditions may expose us to fines, penalties and/or interruptions in our operations that could be material to our results of operations. In addition, emission controls and/or other regulatory or permitting mandates under the CAA and other similar federal and state laws could require unexpected capital expenditures. We cannot assure that existing environmental statutes and regulations will not be revised or that new regulations will not be adopted or become applicable to us. Revised or additional statutes or regulations that result in increased compliance costs or additional operating restrictions could have a material adverse effect on our business, financial condition and results of operations. Our expenditures for environmental investigation and remediation compliance to-date have not been significant in relation to our financial position, results of operations or cash flows, and our expenditures related to environmental matters had no material effects on earnings or cash flows during 2024, 2023 and 2022.

We own or retain legal responsibility for certain environmental conditions at 12 former MGP sites in Kansas. These sites contain contaminants generally associated with MGP sites and are subject to control or remediation under various environmental laws and regulations. A consent agreement with the KDHE governs all environmental investigation and remediation work at these sites. The terms of the consent agreement require us to investigate these sites and set remediation activities based upon the results of the investigations and risk analysis. Remediation typically involves the management of contaminated soils and may involve removal of structures and monitoring and/or remediation of groundwater. We have completed or are addressing removal of the source of soil contamination at all 12 sites and continue to monitor groundwater at seven of the 12 sites according to plans approved by the KDHE. Regulatory closure has been achieved at five of the 12 sites, but these sites remain subject to potential future requirements that may result in additional costs.

We have an AAO that allows Kansas Gas Service to defer and seek recovery of costs necessary for investigation and remediation at, and nearby, these 12 former MGP sites that are incurred after January 1, 2017, up to a cap of $15.0 million, net of any related insurance recoveries. Costs approved for recovery in a future rate proceeding would then be amortized over a 15-year period. The unamortized amounts will not be included in rate base or accumulate carrying charges. Following a determination that future investigation and remediation work approved by the KDHE exceeds $15.0 million, net of any related
insurance recoveries, Kansas Gas Service is required to file an application with the KCC for approval to increase the $15.0 million cap. During 2024, we received $1.7 million in insurance proceeds for remediation costs related to these sites. At December 31, 2024 and December 31, 2023, we have deferred $31.1 million and $32.0 million, respectively, for accrued investigation and remediation costs pursuant to our AAO. On January 3, 2025, Kansas Gas Service requested to increase the cap on the AAO from $15.0 million to $32 million. The original $15.0 million cap approved in 2017 was the result of a unanimous settlement agreement and contained additional reporting requirements and obligations. Kansas Gas Service's request to increase the cap leaves all these additional provisions in place.

We also own or retain legal responsibility for certain environmental conditions at a former MGP site in Texas. At the request of the TCEQ, we began investigating the level and extent of contamination associated with the site under their Texas Risk Reduction Program. A preliminary site investigation revealed that this site contains contaminants generally associated with MGP sites and is subject to control or remediation under various environmental laws and regulations. At December 31, 2024, estimated costs associated with expected remediation activities for this site are not material.

Our expenditures for environmental evaluation, mitigation, remediation and compliance to date have not been significant in relation to our financial position, results of operations or cash flows, and our expenditures related to environmental matters had no material effects on earnings or cash flows during the years ended December 31, 2024, 2023 and 2022. The reserve for remediation of our MGP sites was $14.3 million in December 31, 2024 and December 31, 2023.
Environmental issues may exist with respect to these MGP sites that are unknown to us. Accordingly, future costs are dependent on the final determination and regulatory approval of any remedial actions, the complexity of the site, level of remediation required, changing technology and governmental regulations, and to the extent not recovered by insurance or recoverable in rates from our customers, could be material to our financial condition, results of operations or cash flows.

We are subject to environmental regulation by federal, state and local authorities. Due to the inherent uncertainties surrounding the development of federal and state environmental laws and regulations, we cannot determine with specificity the impact such laws and regulations may have on our existing and future facilities. With the trend toward stricter standards, greater regulation and more extensive permit requirements for the types of assets operated by us, our environmental expenditures could increase in the future, and such expenditures may not be fully recovered by insurance or recoverable in rates from our customers, and those costs may adversely affect our financial condition, results of operations and cash flows.
Pipeline Safety - We are subject to regulation under federal pipeline safety statutes and any analogous state regulations. These include safety requirements for the design, construction, operation, and maintenance of pipelines, including transmission and distribution pipelines. At the federal level, we are regulated by PHMSA. PHMSA regulations require the following for certain pipelines: inspection and maintenance plans; integrity management programs, including the determination of pipeline integrity risks and periodic assessments on certain pipeline segments; an operator qualification program, which includes certain trainings; a public awareness program that provides certain information; and a control room management plan.
As part of the Consolidated Appropriations Act, 2021, the PIPES Act reauthorized PHMSA through 2023 and directed the agency to move forward with several regulatory actions, including the “Pipeline Safety: Class Location Change Requirements” and the “Pipeline Safety: Safety of Gas Transmission and Gathering Pipelines” proposed rulemakings. Congress has also instructed PHMSA to issue final regulations that will require operators of new and existing transmission and distribution pipeline facilities to conduct certain leak detection and repair programs and to require facility inspection and maintenance plans to align with those regulations. To the extent such rulemakings impose more stringent requirements on our facilities, we may be required to incur expenditures that may be material.
Legal Proceedings - We are a party to various litigation matters and claims that have arisen in the normal course of our operations. While the results of litigation and claims cannot be predicted with certainty, we believe the reasonably possible losses from such matters, individually and in the aggregate, are not material. Additionally, we believe the probable outcome of such matters will not have a material adverse effect on our results of operations, financial position or cash flows.
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DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Notes)
 12 Months Ended
Dec. 31, 2024
Fair Value Disclosures [Abstract]  
Fair Value Disclosures DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS
Derivative Instruments - Our derivatives are comprised of over-the-counter natural gas fixed price swaps and call options.

Swaps - At December 31, 2024, we held over-the-counter natural gas fixed-price swaps for the heating season ending March 2025 with a total notional amount of 6.20 Bcf. At December 31, 2023, we held over-the counter natural gas fixed-prices swaps for the heating season ending March 2024 with a total notional amount of 5.1 Bcf.

Options - At December 31, 2024, we held purchased natural gas call options for the heating season ending March 2025 with the total notional amount of 0.60 Bcf, for which we premiums paid of $0.6 million. At December 31, 2023, we held purchased natural gas call options for the heating season ended March 2024 with total notional amount of 0.5 Bcf, for which we paid premiums of $0.5 million.

We have not designated any of our derivative instruments as accounting hedges. These contracts are included in, and recoverable through, our purchased-gas cost adjustment mechanisms. Additionally, premiums paid, changes in fair value and any settlements received associated with these contracts are deferred as part of our unrecovered purchased-gas costs in our consolidated balance sheets. There were no transfers between levels for the periods presented.

Other Financial Instruments - The approximate fair value of cash and cash equivalents, restricted cash and cash equivalents, accounts receivable and accounts payable is equal to book value, due to the short-term nature of these items. Commercial paper is due upon demand and, therefore, the carrying amounts approximate fair value.

The following tables summarize, by level within the fair value hierarchy, our derivative and other assets and liabilities that were accounted for at fair value on a recurring basis at December 31, 2024 and 2023:

December 31, 2024
Level 1Level 2Netting (c)Total
(Thousands of dollars)
Assets:
Derivative instruments - swaps (a)$— $25 $(25)$— 
United States treasury notes (b)8,721 — — 8,721 
Corporate bonds (b)— 13,171 — 13,171 
Total assets$8,721 $13,196 $(25)$21,892 
Liabilities:
Derivative instruments - swaps (a)$— $3,238 $(25)$3,213 
(a) The fair value is included in other current assets and other current liabilities in our consolidated balance sheets.
(b) The fair value is included in other current and noncurrent assets in our consolidated balance sheets.
(c) Our over-the-counter natural gas fixed-price swaps are presented on a net basis when the right of offset exists.

December 31, 2023
Level 1Level 2Total
(Thousands of dollars)
Assets:
United States treasury notes (b)$6,496 $— $6,496 
Corporate bonds (b)— 11,080 11,080 
Total assets$6,496 $11,080 $17,576 
Liabilities:
Derivative instruments - swaps (a)$— $13,920 $13,920 
(a) The fair value is included in other current assets and other current liabilities in our consolidated balance sheets.
(b) The fair value is included in other current and noncurrent assets in our consolidated balance sheets.

The estimated fair value of our long-term debt, including current maturities, was $2.2 billion and $2.8 billion at December 31, 2024 and December 31, 2023, respectively. The estimated fair value of our long-term debt was determined using quoted market prices, and is classified as Level 2.
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VARIABLE INTEREST ENTITES (Notes)
 12 Months Ended
Dec. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Variable Interest Entity Disclosure VARIABLE INTEREST ENTITY
KGSS-I is a special-purpose, wholly owned subsidiary of ONE Gas that was formed for the purpose of issuing securitized bonds to recover extraordinary costs incurred by Kansas Gas Service resulting from Winter Storm Uri. KGSS-I’s assets cannot be used to settle ONE Gas’ obligations and the holders of the Securitized Utility Tariff Bonds have no recourse against ONE Gas. See Note 5 for additional information about the securitization financing.
KGSS-I is considered to be a variable interest entity. As a result, KGSS-I is included in the consolidated financial statements of ONE Gas. No gain or loss was recognized upon initial consolidation.
The following table summarizes the impact of KGSS-I on our consolidated balance sheets:

December 31,
20242023
(Thousands of dollars)
Restricted cash and cash equivalents$20,542 $20,552 
Accounts receivable4,659 5,133 
Securitized intangible asset, net265,951 293,619 
Total assets$291,152 $319,304 
Current maturities of securitized utility tariff bonds28,956 27,430 
Accounts payable319 393 
Accrued interest6,568 7,207 
Securitized utility tariff bonds, excluding current maturities, net of discounts and issuance costs $4.8 million and $5.3 million, as of December 31, 2024 and December 31, 2023, respectively
253,568 282,506 
Equity1,741 1,768 
Total liabilities and equity$291,152 $319,304 

The following table summarizes the impact of KGSS-I on our consolidated statements of income:

Year Ended December 31,
202420232022
(Thousands of dollars)
Operating revenues$44,390 $48,677 $5,769 
Operating expense(443)(440)(52)
Amortization expense(27,668)(30,219)(3,521)
Interest income671 696 6 
Interest expense(16,806)(18,552)(2,202)
Income before income taxes$144 $162 $— 
Income Taxes(26)26 — 
Net Income$118 $188 $— 
The following table summarizes the amortization expense related to the securitized intangible asset expected to be recognized in our consolidated statements of income:

For the year ending:(Thousands of dollars)
2025$29,102 
202630,736 
202732,462 
202834,283 
202936,206 
Thereafter103,162 
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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)
 12 Months Ended
Dec. 31, 2024
Significant Accounting Policies [Line Items]  
Basis of Accounting, Policy
Basis of Presentation - The consolidated financial statements include the accounts of our natural gas distribution business as set forth in “Organization and Nature of Operations” below. All significant balances and transactions between our subsidiaries have been eliminated.
Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies
Organization and Nature of Operations - We provide natural gas distribution services to approximately 2.3 million customers in Oklahoma, Kansas and Texas through our three divisions, Oklahoma Natural Gas, Kansas Gas Service and Texas Gas Service, respectively. We primarily serve residential, commercial and transportation customers in all three states. We are a corporation incorporated under the laws of the state of Oklahoma, and our common stock is listed on the NYSE under the trading symbol “OGS.”
Segments
Segments - We operate in one reportable business segment: regulated public utilities that deliver natural gas primarily to residential, commercial and transportation customers. We define reportable business segments as components of an organization for which discrete financial information is available and operating results are evaluated on a regular basis by the CODM in order to assess performance and allocate resources. Our CODM is our Chief Executive Officer. Characteristics of our organization that were relied upon in making this determination include the similar nature of services we provide, the functional alignment of our organizational structure, and the reports that are regularly reviewed by the CODM for the purpose of assessing performance and allocating resources. Our management is functionally aligned and centralized, with performance evaluated based upon results of the entire distribution business. Capital allocation decisions are driven by asset integrity management, operating efficiency, growth opportunities and government-requested pipeline relocations, not geographic location or regulatory jurisdiction.

In 2024, 2023 and 2022, we had no single external customer from which we received 10 percent or more of our gross revenues.
Revenue [Policy Text Block]
Revenues - We recognize revenue from contracts with customers to depict the transfers of goods and services to customers at an amount that we expect to be entitled to receive in exchange for these goods and services. Our sources of revenue are disaggregated by natural gas sales, transportation revenues, and miscellaneous revenues, which are primarily one-time service fees, that meet the requirements of ASC 606. Certain revenues that do not meet the requirements of ASC 606 are classified as other revenues in our Notes to Consolidated Financial Statements in this Annual Report.

Our natural gas sales to customers and transportation revenues represent revenues from contracts with customers through implied contracts established by our tariffs approved by regulatory authorities. Our customers receive the benefits of our performance when the commodity is delivered to the customer. The performance obligation is satisfied over time as the customer receives the natural gas.

For deliveries of natural gas, customers are billed on a monthly cycle. We recognize revenues upon the delivery of natural gas or services rendered to customers. The billing cycles for customers do not necessarily coincide with the accounting periods used for financial reporting purposes. We accrue unbilled revenues for natural gas that has been delivered but not yet billed at the end of an accounting period. We use the invoice method practical expedient, where we recognize revenue for volumes delivered for which we have a right to invoice. Our estimate of accrued unbilled revenue is based on a percentage estimate of amounts unbilled each month, which is dependent upon a number of factors, some of which require management’s judgment. These factors include customer consumption patterns and the impact of weather on usage. The accrued unbilled natural gas sales revenue is included in accounts receivable on our consolidated balance sheets.

Our miscellaneous revenues from contracts with customers represent implied contracts established by our tariff rates approved by the regulatory authorities and include miscellaneous utility services with the performance obligation satisfied at a point in time when services are rendered to the customer.

Total other revenues consist of revenues associated with regulatory mechanisms that do not meet the requirements of ASC 606 as revenue from contracts with customers, but authorize us to accrue revenues earned based on tariffs approved by regulatory authorities. Other revenues - natural gas sales primarily relate to the WNA mechanism in Kansas. This mechanism adjusts our revenues earned for the variance between actual and normal HDDs. This mechanism can have either positive
(warmer than normal) or negative (colder than normal) effects on revenues.
We collect and remit other taxes on behalf of governmental authorities, and we record these amounts in accrued taxes other than income in our consolidated balance sheets. See Note 2 for additional discussion of revenues.
Use of Estimates
Use of Estimates - The preparation of our consolidated financial statements and related disclosures in accordance with GAAP requires us to make estimates and assumptions with respect to values or conditions that cannot be known with certainty that affect the reported amount of assets and liabilities, and the disclosure of contingent assets and liabilities at the date of the consolidated financial statements. These estimates and assumptions also affect the reported amounts of revenue and expenses during the reporting period. Items that may be estimated include, but are not limited to, the economic useful life of assets, fair value of assets and liabilities, provisions for doubtful accounts receivable, unbilled revenues for natural gas delivered but for which meters have not been read, natural gas purchased but for which no invoice has been received, provision for income taxes, including any deferred income tax valuation allowances, the results of litigation and various other recorded or disclosed amounts.

We evaluate these estimates on an ongoing basis using historical experience and other methods we consider reasonable based on the particular circumstances. Nevertheless, actual results may differ significantly from the estimates. Any effects on our financial position or results of operations from revisions to these estimates are recorded in the period when the facts that give rise to the revision become known.
Cost of Goods and Service
Cost of Natural Gas - Cost of natural gas includes commodity purchases, fuel, storage, transportation, financial derivatives, and other gas purchase costs recovered through our cost of natural gas regulatory mechanisms and does not include an allocation of general operating costs or depreciation and amortization. These cost of natural gas regulatory mechanisms provide a method of recovering natural gas costs on an ongoing basis without a profit. See Note 3 for additional discussion of purchased gas cost recoveries.
Cash and Cash Equivalents, Policy Cash, Cash Equivalents and Restricted Cash and Restricted Cash Equivalents - Cash equivalents and restricted cash equivalents consist of highly liquid investments, which are readily convertible into cash and have original maturities of three months or less. At December 31, 2024, we held $45.4 million in highly liquid investments. Highly liquid investments were not material at December 31, 2023. Restricted cash consists of funds that are contractually or legally restricted as to usage or withdrawal and have been presented separately from cash and cash equivalents on our consolidated balance sheets. Restricted cash and restricted cash equivalents accounts were established for payment of Securitized Utility Tariff Bond issuance costs and payment of debt service on those bonds.
Property, Plant and Equipment Disclosure
Property, Plant and Equipment - Our properties are stated at cost, which includes direct construction costs such as direct labor, materials, burden and AFUDC. Generally, the cost of our property retired or sold, plus removal costs, less salvage, is charged to accumulated depreciation. Gains and losses from sales or retirement of an entire operating unit or system of our properties are recognized in income. Maintenance and repairs are charged directly to expense.

AFUDC represents the cost of borrowed funds used to finance construction activities. We capitalize interest costs during the construction or upgrade of qualifying assets. Capitalized interest is recorded as a reduction to interest expense, net.

Our properties are depreciated using the straight-line method over their estimated useful lives. Generally, we apply composite depreciation rates to functional groups of property having similar economic circumstances. We periodically conduct depreciation studies to assess the economic lives of our assets. These depreciation studies are completed as a part of our regulatory proceedings, and the changes in economic lives, if applicable, are implemented prospectively when the new rates are approved by our regulators and become effective. Changes in the estimated economic lives of our property, plant and equipment could have a material effect on our financial position, results of operations or cash flows.

Property, plant and equipment on our consolidated balance sheets includes construction work in process for capital projects that have not yet been placed in service and therefore are not being depreciated. Assets are transferred out of construction work in process when they are substantially complete and ready for their intended use.

See Note 14 for additional information regarding our property, plant and equipment.
Accounts Receivable
Accounts Receivable, Net - Accounts receivable represent valid claims against nonaffiliated customers for natural gas sold or services rendered. We assess the creditworthiness of our customers. Those customers who do not meet minimum standards may be required to provide security, including deposits and other forms of collateral, when appropriate and allowed by our tariffs. With approximately 2.3 million customers across three states, we are not exposed materially to a concentration of credit risk. We maintain an allowance for doubtful accounts based upon factors surrounding the credit risk of customers, historical trends, consideration of the current environment and other information. We recover natural gas costs related to accounts written off
when they are deemed uncollectible through the purchased-gas cost adjustment mechanisms in each of our jurisdictions. At December 31, 2024 and 2023, our allowance for doubtful accounts was $14.9 million and $16.1 million, respectively.
Inventory, Policy
Inventories - Natural gas in storage is accounted for on the basis of weighted-average cost. Materials and supplies inventories are stated at the lower of weighted-average cost or net realizable value.
Lessee, Leases
Leases - We determine if an arrangement is a lease at inception if the contract conveys the right to control the use and obtain substantially all the economic benefits from the use of an identified asset for a period of time in exchange for consideration. We identify a lease as a finance lease if the agreement includes any of the following criteria: transfer of ownership by the end of the lease term; an option to purchase the underlying asset that the lessee is reasonably certain to exercise; a lease term that represents 75 percent or more of the remaining economic life of the underlying asset; a present value of lease payments and any residual value guaranteed by the lessee that equals or exceeds 90 percent of the fair value of the underlying asset; or an underlying asset that is so specialized in nature that there is no expected alternative use to the lessor at the end of the lease term. A lease that does not meet any of these criteria is considered an operating lease.

Lease right-of-use assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. Right-of-use assets and liabilities are recognized at the commencement date of a lease based on the present value of lease payments over the lease term. Our lease terms may include options to extend or terminate the lease. We include these extension or termination options in the determination of the lease term when it is reasonably certain that we will exercise that option. We have lease agreements with lease and non-lease components, which are accounted for separately. Additionally, for certain office equipment leases, we apply a portfolio approach to effectively account for the operating lease right-of-use assets and liabilities. We do not recognize leases having a term of less than one year in our consolidated balance sheets.

For purposes of determining the present value of the lease payments, we use a lease’s implicit interest rate when readily determinable. As most of our leases do not provide an implicit interest rate, we use an incremental borrowing rate based on available information at the commencement of the lease. Lease cost for operating leases is recognized on a straight-line basis over the lease term. See Note 6 for additional information regarding our leases.
Derivatives, Policy
Derivatives and Risk Management Activities - We record all derivative instruments at fair value, with the exception of certain commodity purchase contracts for which we have chosen the normal purchase normal sale election as they are expected to result in physical delivery. The accounting for changes in the fair value of a derivative instrument depends on whether it has been designated and qualifies as part of a hedging relationship and, if so, the reason for holding it, or if regulatory requirements impose a different accounting treatment.

If certain conditions are met, we may elect to designate a derivative instrument as a hedge of exposure to changes in fair values or cash flows. We have not elected to designate any of our derivative instruments as hedges.

The table below summarizes the various ways in which we account for our derivative instruments and the impact on our consolidated financial statements:
  Recognition and Measurement
Accounting Treatment Balance Sheet Income Statement
Normal purchases and normal sales-Fair value not recorded-Change in fair value not recognized in earnings
Mark-to-market-Recorded at fair value-Change in fair value recognized in, and recoverable through, the purchased-gas cost adjustment mechanisms

See Note 16 for additional information regarding our economic hedging activities using derivatives.
Fair Value Measurement
Fair Value Measurements - We define fair value as the price that would be received from the sale of an asset or the transfer of a liability in an orderly transaction between market participants at the measurement date. We use the market and income approaches to determine the fair value of our assets and liabilities and consider the markets in which the transactions are executed. We measure the fair value of a group of financial assets and liabilities consistent with how a market participant would price the net risk exposure at the measurement date.
Fair Value Hierarchy - At each balance sheet date, we utilize a fair value hierarchy to classify fair value amounts recognized or disclosed in our consolidated financial statements based on the observability of inputs used to estimate such fair value. The levels of the hierarchy are described below:

•Level 1 - Unadjusted quoted prices in active markets for identical assets or liabilities;
•Level 2 - Significant observable pricing inputs other than quoted prices included within Level 1 that are, either directly or indirectly, observable as of the reporting date. Essentially, this represents inputs that are derived principally from or corroborated by observable market data; and
•Level 3 - May include one or more unobservable inputs that are significant in establishing a fair value estimate. These unobservable inputs are developed based on the best information available and may include our own internal data.

We recognize transfers into and out of the levels as of the end of each reporting period.

Determining the appropriate classification of our fair value measurements within the fair value hierarchy requires management’s judgment regarding the degree to which market data is observable or corroborated by observable market data. We categorize derivatives for which fair value is determined using multiple inputs within a single level, based on the lowest level input that is significant to the fair value measurement in its entirety. See Note 16 for additional information regarding our fair value measurements.
Goodwill and Intangible Assets, Policy
Impairment of Goodwill and Long-Lived Assets - We assess our goodwill for impairment at least annually as of July 1, unless events or a change in circumstances indicate an impairment may have occurred before that time. As part of our goodwill impairment test, we first assess qualitative factors (including macroeconomic conditions, industry and market considerations, cost factors and overall financial performance) to determine whether it is more likely than not that our fair value is less than the carrying amount of our net assets. If further testing is necessary or a quantitative test is elected to refresh our recurring qualitative assessment, we perform a quantitative impairment test for goodwill.

Our impairment assessment is performed by comparing our fair value with our book value, including goodwill. If the fair value is less than the book value, an impairment is measured by the amount of our carrying value that exceeds fair value, not to exceed the carrying amount of our goodwill.

To estimate fair value, we use two generally accepted valuation approaches, an income approach and a market approach, using assumptions consistent with a market participant’s perspective. Under the income approach, we use anticipated cash flows over a period of years plus a terminal value and discount these amounts to their present value using appropriate discount rates. Under the market approach, we apply acquisition multiples to forecasted cash flows. The acquisition multiples used are consistent with historical market transactions. The forecasted cash flows are based on average forecasted cash flows over a period of years.

Our goodwill impairment analysis performed in 2024 and 2023 utilized a qualitative assessment and did not result in any impairment indicators, nor did our analysis reflect our reporting unit at risk. Subsequent to July 1, 2024, no event has occurred indicating that it is more likely than not that our fair value is less than the carrying value of our net assets.

We assess our long-lived assets for impairment whenever events or changes in circumstances indicate that an asset’s carrying amount may not be recoverable. An impairment is indicated if the carrying amount of a long-lived asset exceeds the sum of the undiscounted future cash flows expected to result from the use and eventual disposition of the asset. If an impairment is indicated, we record an impairment loss equal to the difference between the carrying value and the fair value of the long-lived asset. We determined that there were no material asset impairments in 2024, 2023 or 2022.
Intangible Assets, Finite-Lived, Policy
Securitized Intangible Asset - On November 18, 2022, KGSS-I acquired the Securitized Utility Tariff Property from Kansas Gas Service for $327.4 million. The Securitized Utility Tariff Property is classified as a securitized intangible asset on our consolidated balance sheets. This securitized intangible asset will be amortized over 10 years, the estimated period needed to collect the required amounts from Kansas Gas Service’s customers to service the Securitized Utility Tariff Bonds. The amortization expense related to the securitized intangible asset will be included in depreciation and amortization expense in our consolidated statements of income. For the years ended December 31, 2024 and 2023, we recorded $27.7 million and $30.2 million, respectively, of amortization expense related to the securitized intangible asset. At the end of its life, this securitized intangible asset will have no residual value. See Note 5 for additional information about the Securitized Utility Tariff Bonds.

Finite-lived intangible assets are stated at cost, net of accumulated amortization, which is recorded on a straight-line or accelerated basis over the life of the asset. We review amortizable intangible assets for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. If such a review should indicate that
the carrying amount of amortizable intangible assets is not recoverable, we reduce the carrying amount of such assets to fair value.
Public Utilities, Policy
Regulation - We are subject to the rate regulation and accounting requirements of the OCC, KCC, RRC and various municipalities in Texas. We follow the accounting and reporting guidance for regulated operations, including evaluating regulatory decisions to determine appropriate revenue recognition, cost deferrals and recoverability for regulatory assets and refund requirements for regulatory liabilities. During the ratemaking process, regulatory authorities set the framework for what we can charge customers for our services and establish the manner that our costs are accounted for, including allowing us to defer recognition of certain costs and permitting recovery of the amounts through rates over time, as opposed to expensing such costs as incurred. Examples include weather normalization, unrecovered purchased-gas costs, extraordinary costs associated with Winter Storm Uri, pension and postemployment benefit costs and ad-valorem taxes. This allows us to stabilize rates over time rather than passing such costs on to the customer for immediate recovery. Actions by regulatory authorities could have an effect on the amount recovered from customers. Any difference in the amount recoverable and the amount deferred is recorded as income or expense at the time of the regulatory action. A write-off of regulatory assets and costs not recovered may be required if all or a portion of the regulated operations have rates that are no longer:

•established by independent regulators;
•designed to recover our costs of providing regulated services; and
•set at levels that will recover our costs when considering the demand and competition for our services.

Should recovery cease due to regulatory actions, certain of these assets may no longer meet the criteria for recognition and accordingly, a write-off of regulatory assets and stranded costs may be required. There were no write-offs of regulatory assets resulting from the failure to meet the criteria for capitalization during 2024, 2023 and 2022.

See Note 3 for additional information regarding our regulatory assets and liabilities.
Postemployment Benefit Plans, Policy
Pension and Other Postemployment Employee Benefits - We have defined benefit pension plans covering eligible employees, all of which are closed to new participants. We also sponsor welfare plans that provide other postemployment medical and life insurance benefits to eligible employees who retire with at least five years of service. To calculate the costs and liabilities related to our plans, we utilize an outside actuarial consultant, which uses statistical and other factors to anticipate future events. These factors include assumptions about the discount rate, expected return on plan assets, rate of future compensation increases, age and mortality and employment periods. We use tables issued by the Society of Actuaries to estimate mortality rates. In determining the projected benefit obligations and costs, assumptions can change from period to period and may result in material changes in the cost and liabilities we recognize.
Income Tax, Policy
Income Taxes - Deferred income taxes are recorded for the difference between the financial statement and income tax basis of assets and liabilities and carryforward items, based on income tax laws and rates existing at the time the temporary differences are expected to reverse. The effect on deferred income taxes of a change in tax rates is deferred and amortized for operations regulated by the OCC, KCC, RRC and various municipalities in Texas, if, as a result of an action by a regulator, it is probable that the effect of the change in tax rates will be recovered from or returned to customers through future rates. We continue to amortize previously deferred investment tax credits for ratemaking purposes over the periods prescribed by our regulators.

A valuation allowance for deferred income tax assets is recognized when it is more likely than not that some or all of the benefit from the deferred income tax asset will not be realized. To assess that likelihood, we use estimates and judgment regarding our future taxable income, as well as the jurisdiction in which such taxable income is generated, to determine whether a valuation allowance is required. Such evidence can include our current financial position, our results of operations, both actual and forecasted, the reversal of deferred income tax liabilities, as well as the current and forecasted business economics of our industry. We had no valuation allowance at December 31, 2024 and 2023.

We utilize a more-likely-than-not recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position that is taken or expected to be taken in a tax return. We reflect penalties and interest as part of income tax expense as they become applicable for tax provisions that do not meet the more-likely-than-not recognition threshold and measurement attribute. There were no material uncertain tax positions at December 31, 2024 and 2023.

Changes in tax laws or tax rates are recognized in the financial reporting period that includes the enactment date.

See Note 12 for additional information regarding income taxes.
Asset Retirement Obligation
Asset Retirement Obligations - Asset retirement obligations represent legal obligations associated with the retirement of long-lived assets that result from the acquisition, construction, development and/or normal use of the asset. Certain long-lived assets that comprise our natural gas distribution systems, primarily our pipeline assets, are subject to agreements or regulations that give rise to an asset retirement obligation for removal or other disposition costs associated with retiring the assets in place upon the discontinued use of the natural gas distribution system. We recognize the fair value of a liability for an asset retirement obligation in the period when it is incurred if a reasonable estimate of the fair value can be made. We are not able to estimate reasonably the fair value of the asset retirement obligations for portions of our assets because the settlement dates are indeterminable given our expected continued use of the assets with proper maintenance. We expect our natural gas distribution systems will continue in operation for the foreseeable future. Based on our proximity to significant natural gas reserves and infrastructure and the widespread use of natural gas for heating and cooking activities by residential and commercial customers in our service areas, we expect supply and demand to exist for the foreseeable future.

In accordance with long-standing regulatory treatment, we collect through rates the estimated costs of removal on certain regulated properties through depreciation expense as a portion of the net salvage value component of our composite deprecation rates, with a corresponding credit to accumulated depreciation and amortization. These removal costs collected through our rates include costs attributable to legal and nonlegal removal obligations. These costs are addressed prospectively in depreciation rates in each general rate order.
For financial reporting purposes, if the removal costs collected have exceeded our removal costs incurred, we estimate a regulatory liability using current rates since the last general rate order in each of our jurisdictions. At December 31, 2024 and 2023, we have recorded a regulatory liability, as our removal costs incurred are less than amounts collected through our depreciation rates in one of our service territories. Significant uncertainty exists regarding the recording of these regulatory liabilities, pending, among other issues, clarification of regulatory intent. We continue to monitor the regulatory requirements, and the regulatory liabilities incurred may be adjusted as more information is obtained. To the extent these estimated liabilities are adjusted, such amounts will be reclassified between accumulated depreciation and amortization and regulatory liabilities on our balance sheet and therefore will not have an impact on earnings.
Commitments and Contingencies, Policy
Contingencies - Our accounting for contingencies covers a variety of business activities, including contingencies for legal and environmental exposures. We accrue these contingencies when our assessments indicate that it is probable that a liability has been incurred or an asset will not be recovered and an amount can be estimated reasonably. We expense legal fees as incurred and base our legal liability estimates on currently available facts and our estimates of the ultimate outcome or resolution. Accruals for the estimated cost of environmental remediation obligations generally are recognized no later than the completion of a remediation feasibility study. Recoveries of environmental remediation costs from other parties are recorded as assets when their receipt is deemed probable. Actual results may differ from our estimates resulting in an impact, positive or negative, on earnings.

See Note 15 for additional information regarding contingencies.
Share-Based Payment Arrangement
Share-Based Payments - We expense the fair value of share-based payments net of estimated forfeitures. We estimate forfeiture rates based on historical forfeitures under our share-based payment plans.
Earnings Per Share, Policy
Earnings per share - Basic EPS is calculated by dividing net income by the daily weighted-average number of common shares outstanding during the periods presented, which includes fully vested stock awards that have not yet been issued as common stock. Diluted EPS is based on shares outstanding for the calculation of basic EPS, plus unvested stock awards granted under our compensation plans and equity forward sale agreements, but only to the extent these instruments dilute earnings per share.
Reclassification, Comparability Adjustment
Reclassifications - Reclassifications have been made in the prior-year financial statements to conform to the current-year presentation. We have updated our consolidated balance sheet at December 31, 2023, to disaggregate the following line items from their previous presentation to conform to our current-year presentation: “income tax receivable” from “other current assets” and “pension and other postemployment benefits” from “other assets.” We have also updated our consolidated balance sheet at December 31, 2023, to include “employee benefit obligations” within “other deferred credits.”
Recently Issued Accounting Standards Update
Recently Issued Accounting Standards Update - In November 2024, the FASB issued ASU-2024-03, “Disaggregation of Income Statement Expenses (Subtopic 220-40).” The amendments in this standard address requests from investors for more detailed information about the types of expenses commonly presented in income statements and will require a footnote disclosure to disaggregate, in a tabular presentation, each relevant expense category on the face of the income statement that includes any of the following natural expenses: purchases of inventory, employee compensation, depreciation, intangible asset amortization, and depreciation, depletion, and amortization recognized as part of oil- and gas-producing activities or other types of depletion expenses. The amendments in this update are effective for annual periods beginning after December 15, 2026, and
interim periods within annual periods beginning after December 15, 2027. We are currently assessing the timing and impacts of adopting this standard.

In December 2023, the FASB issued ASU 2023-09, “Income Taxes (Topic 740): Improvements to Income Tax Disclosures,” which is intended to enhance annual income tax disclosures to address investor requests for more information about the tax risks and opportunities present in an entity’s operations. The amendments in this standard require disclosure of additional information in specified categories with respect to the reconciliation of the effective tax rate to the statutory rate (the rate reconciliation) for federal, state, and foreign income taxes. They also require greater detail about individual reconciling items in the rate reconciliation to the extent the impact of those items exceeds a specified threshold. In addition to new disclosures associated with the rate reconciliation, the amendments in this update require information pertaining to taxes paid (net of refunds received) to be disaggregated for federal, state, and foreign taxes and further disaggregated for specific jurisdictions to the extent the related amounts exceed a quantitative threshold. The amendments in this update are effective for annual periods beginning after December 15, 2024. We adopted this guidance for 2024 — earlier than the effective date. Our adoption did not result in a material impact to our consolidated financial statements. See Note 12 for additional information regarding income taxes.

In November 2023, the FASB issued ASU 2023-07, “Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures,” which is intended to improve annual and interim reportable segment disclosure requirements, primarily through enhanced disclosures about significant segment expenses. The amendments in this standard enhance interim disclosure requirements, clarify circumstances in which an entity can disclose multiple segment measures of profit or loss, provide new segment disclosure requirements for entities with a single reportable segment, and contain other disclosure requirements. The amendments in this update are effective for annual periods beginning after December 15, 2023, and interim periods within annual periods beginning after December 15, 2024. We adopted this guidance as of the effective date. Our adoption did not result in a material impact to our consolidated financial statements and disclosures.
v3.25.0.1
REVENUE (Tables)
 12 Months Ended
Dec. 31, 2024
Revenues Disaggregated by Source [Table]
The following table sets forth our revenues disaggregated by source for the periods indicated:

Year Ended December 31,
202420232022
(Thousands of dollars)
Natural gas sales to customers$1,841,400 $2,141,908 $2,410,048 
Transportation revenues137,111 132,945 125,951 
Securitization customer charges (Note 17)
44,390 48,677 5,769 
Miscellaneous revenues22,971 22,791 19,850 
Total revenues from contracts with customers2,045,872 2,346,321 2,561,618
Other revenues - natural gas sales related24,296 12,764 3,403 
Other revenues 13,390 12,905 12,984 
Total other revenues37,686 25,669 16,387 
Total revenues$2,083,558 $2,371,990 $2,578,005 
v3.25.0.1
REGULATORY ASSETS AND LIABILITIES (Tables)
 12 Months Ended
Dec. 31, 2024
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]  
SCHEDULE OF REGULATED ASSETS AND LIABILITIES
The tables below present a summary of regulatory assets and liabilities, net of amortization, for the periods indicated:

December 31, 2024
Recovery PeriodCurrentNoncurrentTotal
(Thousands of dollars)
Winter weather event costs(a)$9,051 $15,938 $24,989 
Under-recovered purchased-gas costs1 year43,819 — 43,819 
Pension and postemployment benefit costs, net
See Note 11
1,358 224,837 226,195 
Reacquired debt costs4 years723 1,989 2,712 
MGP remediation costs15 years1,000 30,067 31,067 
Ad-valorem tax1 year14,066 — 14,066 
WNA1 year26,684 — 26,684 
Customer credit deferrals1 year255 3,639 3,894 
Other, net1 to 20 years4,254 1,536 5,790 
Total regulatory assets101,210 278,006 379,216 
Income tax rate changes(a)— (467,563)(467,563)
Over-recovered purchased-gas costs1 year(22,525)— (22,525)
Total regulatory liabilities(22,525)(467,563)(490,088)
Net regulatory assets and liabilities$78,685 $(189,557)$(110,872)
(a) Recovery period varies by jurisdiction. See discussion below for additional information regarding our regulatory assets related to winter weather event costs and regulatory liabilities related to income tax rate changes.

December 31, 2023
Recovery PeriodCurrentNoncurrentTotal
(Thousands of dollars)
Winter weather event costs(a)$22,633 $21,495 $44,128 
Under-recovered purchased-gas costs1 year10,391 — 10,391 
Pension and postemployment benefit costs
See Note 11
6,379 228,092 234,471 
Reacquired debt costs6 years723 2,712 3,435 
MGP remediation costs15 years98 31,893 31,991 
Ad-valorem tax1 year14,533 — 14,533 
WNA1 year11,404 — 11,404 
Customer credit deferrals1 year6,184 — 6,184 
Other1 to 18 years2,963 3,714 6,677 
Total regulatory assets75,308 287,906 363,214 
Income tax rate changes(a)— (500,478)(500,478)
Over-recovered purchased-gas costs1 year(66,901)— (66,901)
Total regulatory liabilities(66,901)(500,478)(567,379)
Net regulatory assets and liabilities$8,407 $(212,572)$(204,165)
(a) Recovery period varies by jurisdiction. See discussion below for additional information regarding our regulatory assets related to winter weather event costs and regulatory liabilities related to income tax rate changes.
v3.25.0.1
LONG-TERM DEBT (Tables)
 12 Months Ended
Dec. 31, 2024
Long-Term Debt, Unclassified [Abstract]  
Schedule of Long-Term Debt Instruments
The table below presents a summary of our long-term debt outstanding for the periods indicated:

December 31,
Interest Rate
20242023
(Thousands of dollars)
Senior Notes due:
February 20243.610%$— $300,000 
March 20241.100%— 473,000 
April 20295.100%550,000 300,000 
May 20302.000%300,000 300,000 
September 20324.250%300,000 300,000 
February 20444.658%600,000 600,000 
November 20484.500%400,000 400,000 
Total Senior Notes2,150,000 2,673,000 
KGSS-I Securitized Utility Tariff Bonds5.486%287,345 315,284 
Unamortized discounts, net of premiums, on long-term debt(3,624)(7,615)
Debt issuance costs (a)(20,691)(21,092)
Other8.000%1,226 1,238 
Total long-term debt, net2,414,256 2,960,815 
Less: current maturities of KGSS-I securitized utility tariff bonds, net28,956 27,430 
Less: current maturities of other long-term debt, net14 772,984 
Noncurrent portion of long-term debt, net$2,385,286 $2,160,401 
(a) Includes issuance costs and discounts for the KGSS-I Securitized Utility Tariff Bonds of $4.8 million and $5.3 million, at December 31, 2024 and December 31, 2023 respectively.
v3.25.0.1
Leases, (Tables)
 12 Months Ended
Dec. 31, 2024
Leases [Abstract]  
Other Information Related to Operating Leases Table Text Block
Year Ended
December 31,
Other information related to operating leases202420232022
(Millions of dollars)
Weighted-average remaining lease term4 years4 years5 years
Weighted-average discount rate4.37 %4.28 %4.04 %
Supplemental cash flows information
Lease payments$(7.9)$(8.3)$(8.2)
Right-of-use assets obtained in exchange for lease obligations$2.7 $3.9 $0.3 
Lessee, Operating Lease, Liability, to be Paid, Maturity
December 31,
Future minimum lease payments under non-cancellable operating leases2024
(Millions of dollars)
2025$5.9 
20264.3 
20273.3 
20283.0 
20291.5 
Thereafter— 
Total future minimum lease payments$18.0 
Imputed interest(1.4)
Total operating lease liability$16.6 
Consolidated balance sheets as of December 31, 2024
Current operating lease liability$5.2 
Long-term operating lease liability11.4 
Total operating lease liability$16.6 
v3.25.0.1
Equity (Tables)
 12 Months Ended
Dec. 31, 2024
Equity [Abstract]  
Schedule of Forward Contracts Indexed to Issuer's Equity
The following table summarizes all of our outstanding forward sale agreements at December 31, 2024:

MaturityOriginal SharesRemaining SharesForward PriceNet Proceeds Available
(Shares)(Shares)(Per share)(Thousands of dollars)
December 31, 20251,200,000 223,000 $74.65 $16,647 
December 31, 2025180,000 180,000 74.60 13,428 
Total forward sale agreements1,380,000 403,000 $74.63 $30,075 
v3.25.0.1
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)
 12 Months Ended
Dec. 31, 2024
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]  
Schedule of Accumulated Other Comprehensive Income (Loss)
The following table sets forth the balance in accumulated other comprehensive loss for the periods indicated:

Accumulated Other Comprehensive Loss
(Thousands of dollars)
January 1, 2023$(704)
Pension plan obligation
Other comprehensive income (loss) before reclassification, net of tax of $140
(477)
Amounts reclassified from accumulated other comprehensive loss, net of tax of $—
(1)
Other comprehensive income (loss)(478)
December 31, 2023(1,182)
Pension plan obligation
Other comprehensive income (loss) before reclassification, net of tax of $(281)
961 
Amounts reclassified from accumulated other comprehensive loss, net of tax of $—
(1)
Available-for-sale securities
Other comprehensive income (loss) before reclassification, net of tax of $(24)
94 
Amounts reclassified from accumulated other comprehensive loss, net of tax of $(1)
2 
Other comprehensive income (loss)1,056 
December 31, 2024$(126)
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]
The following table sets forth the effect of reclassifications from accumulated other comprehensive loss in our consolidated statements of income for the periods indicated:

Year EndedAffected Line Item in the
Details About Accumulated Other December 31,Consolidated Statements
Comprehensive Loss Components202420232022of Income
(Thousands of dollars)
Pension and other postemployment benefit plan obligations (a)
Amortization of net gain (loss)$(5,770)$(1,960)$(17,010)
Amortization of unrecognized prior service credit (cost)(372)(525)(289)
(6,142)(2,485)(17,299)
Regulatory adjustments (b)6,143 2,486 17,141 
Amounts reclassified from accumulated other comprehensive loss1 1 (158)Other income (expense), net
Available-for-sale securities
Amounts reclassified from accumulated other comprehensive loss(3)— — Other income (expense), net
Total available-for-sale securities(3)— — 
Total reclassifications before tax(2)1 (158)Income before income taxes
Tax effect of reclassifications1 — 36 Income tax expense
Net reclassifications for the period$(1)$1 $(122)Net income
(a) These components of accumulated other comprehensive loss are included in the computation of net periodic benefit credit. See Note 11 for additional detail of our net periodic benefit credit.
(b) Regulatory adjustments represent pension and other postemployment benefit credits or costs expected to be recovered through rates and are deferred as part of our regulatory assets. See Note 3 for additional disclosures of regulatory assets and liabilities.
v3.25.0.1
EARNINGS PER SHARE (Tables)
 12 Months Ended
Dec. 31, 2024
EARNINGS PER SHARE [Line Items]  
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]
The following tables set forth the computation of basic and diluted EPS from continuing operations for the periods indicated:

Year Ended December 31, 2024
IncomeSharesPer Share
Amount
(Thousands, except per share amounts)
Basic EPS Calculation
Net income available for common stock
$222,850 56,826 $3.92 
Diluted EPS Calculation
Effect of dilutive securities— 207 
Net income available for common stock and common stock equivalents$222,850 57,033 $3.91 
Year Ended December 31, 2023
IncomeSharesPer Share
Amount
(Thousands, except per share amounts)
Basic EPS Calculation
Net income available for common stock
$231,232 55,600 $4.16 
Diluted EPS Calculation
Effect of dilutive securities— 260 
Net income available for common stock and common stock equivalents$231,232 55,860 $4.14 
Year Ended December 31, 2022
IncomeSharesPer Share
Amount
(Thousands, except per share amounts)
Basic EPS Calculation
Net income available for common stock
$221,742 54,207 $4.09 
Diluted EPS Calculation
Effect of dilutive securities— 131 
Net income available for common stock and common stock equivalents$221,742 54,338 $4.08 
v3.25.0.1
Compensation Related Costs, Share Based Payments (Tables)
 12 Months Ended
Dec. 31, 2024
Share-Based Payment Arrangement [Abstract]  
Share-Based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity The following tables set forth activity and various statistics for restricted stock unit awards outstanding under the respective plans for the period indicated:
Number of
Units		Weighted-
Average Grant Date Fair Value
Nonvested at December 31, 2023
126,948 $77.50 
Granted67,432 60.74 
Vested(41,168)72.46 
Forfeited(4,175)71.40 
Nonvested at December 31, 2024
149,037 $68.79 

 202420232022
Weighted-average grant date fair value (per share)
$60.74 $81.79 $76.96 
Fair value of shares granted (thousands of dollars)
$4,096 $3,995 $4,342 
Schedule of Nonvested Performance-Based Units Activity The following tables set forth activity and various statistics related to our performance stock unit awards and the assumptions used by us in the valuations of the 2024, 2023 and 2022 grants at the grant date:
Number of
Units		Weighted-
Average Grant Date Fair Value
Nonvested at December 31, 2023
247,326 $95.23 
Granted139,727 67.83 
Vested— — 
Forfeited(81,568)82.85 
Nonvested at December 31, 2024
305,485 $86.00 
202420232022
Volatility (a)26.63% 29.20%34.00%
Dividend yield4.35%3.18%3.22%
Risk-free interest rate (b)4.46%4.37%1.65%
(a) - Volatility based on historical volatility over three years using daily stock price observations of our peer utilities.
(b) - Using 3-year treasury rate.

202420232022
Weighted-average grant date fair value (per share)
$67.83 $105.74 $95.80 
Fair value of shares granted (thousands of dollars)
$9,478 $10,095 $8,360 
v3.25.0.1
EMPLOYEE BENEFIT PLANS (Tables)
 12 Months Ended
Dec. 31, 2024
Employee Benefit Plans [Line Items]  
Defined Benefit Plan, Assumptions
Actuarial Assumptions - The following table sets forth the weighted-average assumptions used to determine benefit obligations for pension and postemployment benefits for the periods indicated:

December 31,
 20242023
Discount rate - pension plans5.70%5.30%
Discount rate - other postemployment plans5.75%5.40%
Compensation increase rate
 3.50% - 4.30%
3.50% - 4.30%
The following table sets forth the weighted-average assumptions used by us to determine the periodic benefit costs for pension and postemployment benefits for the periods indicated:

Year Ended December 31,
 202420232022
Discount rate - pension plans5.30%5.60%
3.05%/4.55% (a)
Discount rate - other postemployment plans5.40%5.70%3.00%
Expected long-term return on plan assets - pension plans6.70%6.75%6.40%
Expected long-term return on plan assets - other postemployment plans5.20%5.55%5.85%
Compensation increase rate
3.50% - 4.30%
3.60% - 5.00%
3.10% - 5.00%
(a) Pension plans were remeasured as of April 30, 2022.
Schedule of Defined Benefit Plans Disclosures
Obligations and Funded Status - The following table sets forth our defined benefit pension and other postemployment benefit plans, benefit obligations and fair value of plan assets for the periods indicated:

Pension BenefitsOther Postemployment Benefits
December 31, December 31,
2024202320242023
Changes in Benefit Obligation(Thousands of dollars)
Benefit obligation, beginning of period$803,605 $784,633 $158,535 $168,342 
Service cost6,204 7,242 610 730 
Interest cost41,123 42,428 8,179 9,154 
Plan participants’ contributions— — 2,631 2,823 
Actuarial loss (gain)
(27,026)23,015 (3,267)(5,551)
Benefits paid
(54,099)(53,713)(15,704)(16,963)
Settlements(38,690)— — — 
Benefit obligation, end of period$731,117 $803,605 $150,984 $158,535 
Change in Plan Assets
Fair value of plan assets, beginning of period$795,381 $768,961 $181,608 $181,877 
Actual return on plan assets
22,322 78,827 8,404 11,325 
Employer contributions1,559 1,306 — 2,546 
Plan participants’ contributions— — 2,631 2,823 
Benefits paid
(54,099)(53,713)(13,154)(16,963)
Settlements(39,762)— — — 
Fair value of assets, end of period725,401 795,381 179,489 181,608 
Benefit asset (obligation), net
$(5,716)$(8,224)$28,505 $23,073 
Pension and other postemployment benefits$14,377 $13,409 $28,505 $23,073 
Current liabilities(1,409)(1,368)— — 
Noncurrent liabilities(18,684)(20,265)— — 
Benefit asset (obligation), net$(5,716)$(8,224)$28,505 $23,073 
Schedule of Net Benefit Costs [Table Text Block]
The following tables set forth the components of net periodic benefit cost for our pension and other postemployment benefit plans for the periods indicated:

Pension Benefits
Year Ended December 31,
202420232022
(Thousands of dollars)
Components of net periodic benefit cost (credit)
 
Service cost$6,204 $7,242 $10,369 
Interest cost (a)
41,123 42,428 36,150 
Expected return on assets (a)
(59,027)(59,518)(58,528)
Amortization of unrecognized prior service cost (a)
372 372 248 
Amortization of net loss (a)
5,786 2,008 16,793 
Net periodic benefit cost (credit)
$(5,542)$(7,468)$5,032 
(a) These amounts, net of any amounts capitalized as a regulatory asset, have been recognized as other (income) expense, net in the consolidated statement of income. See Note 13 for additional detail.

Other Postemployment Benefits
Year Ended December 31,
202420232022
(Thousands of dollars)
Components of net periodic benefit cost (credit)
Service cost$610 $730 $1,274 
Interest cost (a)
8,179 9,154 6,448 
Expected return on assets (a)
(9,134)(9,728)(13,181)
Amortization of unrecognized prior service cost (credit) (a)
— 153 41 
Amortization of net loss (gain) (a)
(16)(48)217 
Net periodic benefit cost (credit)
$(361)$261 $(5,201)
(a) These amounts, net of any amounts capitalized as a regulatory asset, have been recognized as other (income) expense, net in the consolidated statement of income. See Note 13 for additional detail.
Schedule of Amounts Recognized in Other Comprehensive Income (Loss)
Other Comprehensive Income (Loss) - The following table sets forth the amounts recognized in other comprehensive income (loss), net of regulatory deferrals, related to our defined benefit pension benefits for the period indicated:

Pension Benefits
Year Ended December 31,
202420232022
(Thousands of dollars)
Net gain (loss) arising during the period
$1,242 $(619)$7,369 
Amortization of net loss (gain)(1)1 159 
Deferred income taxes(281)140 (1,705)
   Total recognized in other comprehensive income (loss)
$960 $(478)$5,823 
Schedule of Net Periodic Benefit Cost Not yet Recognized
The tables below set forth the amounts in accumulated other comprehensive loss that had not yet been recognized as components of net periodic benefit credit for the periods indicated:

Pension Benefits
December 31,
20242023
(Thousands of dollars)
Prior service cost$(1,720)$(2,091)
Accumulated loss(251,952)(246,988)
Accumulated other comprehensive loss before regulatory asset(253,672)(249,079)
Regulatory asset for regulated entities253,517 247,684 
Accumulated other comprehensive loss after regulatory asset(155)(1,395)
Deferred income taxes(67)213 
Accumulated other comprehensive loss, net of tax$(222)$(1,182)

Other Postemployment Benefits
December 31,
20242023
(Thousands of dollars)
Prior service cost$— $— 
Accumulated gain (loss)1,065 (1,457)
Accumulated other comprehensive loss before regulatory asset1,065 (1,457)
Regulatory asset for regulated entities(1,065)1,457 
Accumulated other comprehensive loss after regulatory asset$— $— 
Schedule of Health Care Cost Trend Rates
Health Care Cost Trend Rates - The following table sets forth the assumed health care cost-trend rates for the periods indicated:

20242023
Health care cost-trend rate assumed for next year7.00%6.00%
Rate to which the cost-trend rate is assumed to decline (the ultimate trend rate)4.50%4.50%
Year that the rate reaches the ultimate trend rate20352030
Schedule of Allocation of Plan Assets The current target allocation for the assets of our defined benefit pension plan is as follows:
Investment-grade bonds70.0 %
U.S. large-cap equities13.0 %
Alternative investments7.0 %
Developed foreign equities5.0 %
Mid-cap equities3.0 %
Emerging markets equities1.0 %
Small-cap equities1.0 %
  Total100.0 %
Schedule Of Employee Pension Plans Investments At Fair Value
The following tables set forth our pension and other postemployment benefits plan assets by fair value category as of the measurement date:

Pension Benefits
December 31, 2024
Asset CategoryLevel 1Level 2Level 3Total
(Thousands of dollars)
Investments:
Equity securities (a)$81,459 $— $— $81,459 
Government obligations— 213,572 — 213,572 
Corporate obligations (b)— 328,915 — 328,915 
Cash and money market funds (c)5,871 24,737 — 30,608 
Insurance contracts and group annuity contracts— — 11,177 11,177 
Other investments (d)— — 59,670 59,670 
  Total assets$87,330 $567,224 $70,847 $725,401 
(a) - This category represents securities of the various market sectors from diverse industries.
(b) - This category represents bonds from diverse industries.
(c) - This category primarily represents money market funds.
(d) - This category represents alternative investments such as hedge funds and other financial instruments.

Pension Benefits
December 31, 2023
Asset CategoryLevel 1Level 2Level 3Total
(Thousands of dollars)
Investments:
Equity securities (a)$88,477 $— $— $88,477 
Government obligations— 204,669 — 204,669 
Corporate obligations (b)— 366,482 — 366,482 
Cash and money market funds (c)5,300 28,977 — 34,277 
Insurance contracts and group annuity contracts— — 12,350 12,350 
Other investments (d)— — 89,126 89,126 
  Total assets$93,777 $600,128 $101,476 $795,381 
(a) - This category represents securities of the various market sectors from diverse industries.
(b) - This category represents bonds from diverse industries.
(c) - This category primarily represents money market funds.
(d) - This category represents alternative investments such as hedge funds and other financial instruments.

Other Postemployment Benefits
December 31, 2024
Asset CategoryLevel 1Level 2Level 3Total
(Thousands of dollars)
Investments:
Equity securities (a)$7,226 $— $— $7,226 
Government obligations— 41,982 — 41,982 
Corporate obligations (b)— 36,411 — 36,411 
Cash and money market funds (c)806 12,167 — 12,973 
Insurance contracts and group annuity contracts (d)— 80,897 — 80,897 
  Total assets$8,032 $171,457 $— $179,489 
(a) - This category represents securities of the various market sectors from diverse industries.
(b) - This category represents bonds from diverse industries.
(c) - This category primarily represents money market funds.
(d) - This category includes equity securities and bonds held in a captive insurance product.
Other Postemployment Benefits
December 31, 2023
Asset CategoryLevel 1Level 2Level 3Total
(Thousands of dollars)
Investments:
Equity securities (a)$7,031 $— $— $7,031 
Government obligations— 41,863 — 41,863 
Corporate obligations (b)— 38,615 — 38,615 
Cash and money market funds (c)751 13,245 — 13,996 
Insurance contracts and group annuity contracts (d)— 80,102 — 80,102 
  Total assets$7,782 $173,825 $— $181,607 
(a) - This category represents securities of the various market sectors from diverse industries.
(b) - This category represents bonds from diverse industries.
(c) - This category primarily represents money market funds.
(d) - This category includes equity securities and bonds held in a captive insurance product.

Insurance contracts and group annuity contracts include investments in the Immediate Participation Guarantee Fund (“IPG Fund”) with John Hancock and are valued at fair value. John Hancock invests the IPG Fund in its general fund portfolio. The contract value of the IPG Fund at the end of the year, which approximates fair value, is estimated. The difference between this estimated balance and the actual balance, as subsequently determined by John Hancock, is charged or credited to the net assets of the plans.

Certain investments that are categorized as money market funds in Level 2 and other investments in Level 3 represent alternative investments such as hedge funds and other financial instruments measured using the net asset value per share (or its equivalent) practical expedient.

The following tables set forth additional information regarding commitments and redemption limitations of these other investments at the periods indicated:

December 31, 2024
Fair ValueUnfunded CommitmentsRedemption FrequencyRedemption Notice Period
(in thousands)(in days)
Grosvenor Registered Multi Limited Partnership$29,642 $— quarterly65
K2 Institutional Investors II Limited Partnership$30,028 $— quarterly91

December 31, 2023
Fair ValueUnfunded CommitmentsRedemption FrequencyRedemption Notice Period
(in thousands)(in days)
Grosvenor Registered Multi Limited Partnership$40,872 $— quarterly65
K2 Institutional Investors II Limited Partnership$48,254 $— quarterly91
Schedule of Effect of Significant Unobservable Inputs, Changes in Plan Assets
The following table sets forth the reconciliation of Level 3 fair value measurements of our pension plans for the periods indicated:

Pension Benefits
Insurance
Contracts		Other
Investments		Total
(Thousands of dollars)
January 1, 2023$14,480 $87,031 $101,511 
Unrealized gains— 2,095 2,095 
Unrealized losses(618)— (618)
Purchases1,562 — 1,562 
Settlements(3,074)— (3,074)
December 31, 2023$12,350 $89,126 $101,476 
Unrealized gains445 — 445 
Unrealized losses— (2,984)(2,984)
Expense(167)— (167)
Purchases— 1,408 1,408 
Sales— (27,880)(27,880)
Benefits paid(1,451)— (1,451)
December 31, 2024$11,177 $59,670 $70,847 
Schedule of Expected Benefit Payments The following table sets forth the pension benefits and other postemployment benefits payments expected to be paid in 2025-2034:
Pension
Benefits		Other Postemployment
Benefits
Benefits to be paid in:(Thousands of dollars)
2025$52,832 $14,127 
202653,298 13,734 
202753,470 13,431 
202854,189 13,069 
202954,094 12,745 
2030 through 2034271,532 58,985 
v3.25.0.1
Income Taxes (Tables)
 12 Months Ended
Dec. 31, 2024
Income Tax Disclosure [Abstract]  
Schedule of Components of Income Tax Expense (Benefit)
The following table sets forth our provision for income taxes for the periods indicated:

Year Ended December 31,
202420232022
(Thousands of dollars)
Current income tax provision (benefit)
Federal$(68,660)$16,551 $61,745 
State(1,476)(829)6,815 
Total current income tax provision (benefit)(70,136)15,722 68,560 
Deferred income tax provision (benefit)
Federal110,717 21,905 (22,234)
State(4,195)2,868 200 
Total deferred income tax provision (benefit)106,522 24,773 (22,034)
Total provision for income taxes$36,386 $40,495 $46,526 
Schedule of Effective Income Tax Rate Reconciliation
The following table is a reconciliation of our income tax provision for the periods indicated:

Year Ended December 31,
202420232022
(Thousands of dollars, except percentages)
Income before income taxes$259,236 $271,727 $268,268 
Federal statutory income tax rate21 %21 %21 %
Provision for federal income taxes54,439 21%57,063 21%56,335 21%
State income taxes, net of federal tax benefit4,333 2%3,834 1%7,016 3%
Tax effect of permanent differences2,018 1%1,860 1%1,369 1%
Tax effect of state income tax deduction(209)—%(443)—%(1,254)—%
Amortization of excess deferred federal income taxes(15,680)(6)%(20,565)(8)%(17,986)(7)%
Amortization of excess deferred state income taxes(10,004)(4)%(1,795)(1)%— —%
Tax (expense) benefit for employee share-based compensation1,063 —%418 —%350 —%
Other, net426 —%123 —%696 —%
Total provision for income taxes and effective income tax rate$36,386 14%$40,495 14%$46,526 18%
Schedule of Deferred Tax Assets and Liabilities
The following table sets forth the tax effects of temporary differences that gave rise to significant portions of the deferred tax assets and liabilities for the periods indicated:

December 31,
20242023
(Thousands of dollars)
Deferred tax assets
Employee benefits and other accrued liabilities$— $— 
Regulatory adjustments for enacted tax rate changes100,718 107,948 
Net operating loss405,316 93,255 
Lease obligation basis3,669 4,500 
Purchased-gas cost adjustment— 5,232 
Other— — 
Total deferred tax assets509,703 210,935 
Deferred tax liabilities
Excess of tax over book depreciation930,680 822,619 
Winter weather event costs381,818 56,914 
Purchased-gas cost adjustment8,654 — 
Other regulatory assets and liabilities, net73,904 70,384 
Employee benefits and other accrued liabilities934 205 
Right-of-use asset basis3,866 4,662 
Other1,585 8,219 
Total deferred tax liabilities1,401,441 963,003 
Net deferred tax liabilities$891,738 $752,068 
v3.25.0.1
OTHER INCOME AND OTHER EXPENSE (Tables)
 12 Months Ended
Dec. 31, 2024
Schedule of Other Nonoperating Income (Expense)
The following table sets forth the components of other income and other expense for the periods indicated:

Year Ended December 31,
202420232022
(Thousands of dollars)
Net periodic benefit credit other than service cost
$3,600 $4,017 $3,766 
Gain (loss) on investments associated with nonqualified deferred compensation plans
3,653 4,826 (7,197)
Other income (expense), net174 633 (752)
Total other income, net
$7,427 $9,476 $(4,183)
v3.25.0.1
Property, Plant, and Equipment (Tables)
 12 Months Ended
Dec. 31, 2024
Property, Plant and Equipment [Abstract]  
Public Utility Property, Plant, and Equipment
The following table sets forth our property, plant and equipment by property type, for the periods indicated:

December 31,
20242023
(Thousands of dollars)
Natural gas distribution pipelines and related equipment$7,278,542 $6,716,074 
Natural gas transmission pipelines and related equipment736,229 713,505 
General plant and other942,677 907,946 
Construction work in process166,686 131,442 
Property, plant and equipment9,124,134 8,468,967 
Accumulated depreciation and amortization(2,478,261)(2,333,755)
Net property, plant and equipment$6,645,873 $6,135,212 
v3.25.0.1
DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Tables)
 12 Months Ended
Dec. 31, 2024
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value Measurements, Recurring and Nonrecurring
The following tables summarize, by level within the fair value hierarchy, our derivative and other assets and liabilities that were accounted for at fair value on a recurring basis at December 31, 2024 and 2023:

December 31, 2024
Level 1Level 2Netting (c)Total
(Thousands of dollars)
Assets:
Derivative instruments - swaps (a)$— $25 $(25)$— 
United States treasury notes (b)8,721 — — 8,721 
Corporate bonds (b)— 13,171 — 13,171 
Total assets$8,721 $13,196 $(25)$21,892 
Liabilities:
Derivative instruments - swaps (a)$— $3,238 $(25)$3,213 
(a) The fair value is included in other current assets and other current liabilities in our consolidated balance sheets.
(b) The fair value is included in other current and noncurrent assets in our consolidated balance sheets.
(c) Our over-the-counter natural gas fixed-price swaps are presented on a net basis when the right of offset exists.

December 31, 2023
Level 1Level 2Total
(Thousands of dollars)
Assets:
United States treasury notes (b)$6,496 $— $6,496 
Corporate bonds (b)— 11,080 11,080 
Total assets$6,496 $11,080 $17,576 
Liabilities:
Derivative instruments - swaps (a)$— $13,920 $13,920 
(a) The fair value is included in other current assets and other current liabilities in our consolidated balance sheets.
(b) The fair value is included in other current and noncurrent assets in our consolidated balance sheets.
v3.25.0.1
VARIABLE INTEREST ENTITES (Tables)
 12 Months Ended
Dec. 31, 2024
Variable Interest Entity [Line Items]  
Schedule of Finite-Lived Intangible Assets
The following table summarizes the amortization expense related to the securitized intangible asset expected to be recognized in our consolidated statements of income:

For the year ending:(Thousands of dollars)
2025$29,102 
202630,736 
202732,462 
202834,283 
202936,206 
Thereafter103,162 
Kansas Gas Service Securitization I LLC  
Variable Interest Entity [Line Items]  
Schedule of Variable Interest Entities
The following table summarizes the impact of KGSS-I on our consolidated balance sheets:

December 31,
20242023
(Thousands of dollars)
Restricted cash and cash equivalents$20,542 $20,552 
Accounts receivable4,659 5,133 
Securitized intangible asset, net265,951 293,619 
Total assets$291,152 $319,304 
Current maturities of securitized utility tariff bonds28,956 27,430 
Accounts payable319 393 
Accrued interest6,568 7,207 
Securitized utility tariff bonds, excluding current maturities, net of discounts and issuance costs $4.8 million and $5.3 million, as of December 31, 2024 and December 31, 2023, respectively
253,568 282,506 
Equity1,741 1,768 
Total liabilities and equity$291,152 $319,304 

The following table summarizes the impact of KGSS-I on our consolidated statements of income:

Year Ended December 31,
202420232022
(Thousands of dollars)
Operating revenues$44,390 $48,677 $5,769 
Operating expense(443)(440)(52)
Amortization expense(27,668)(30,219)(3,521)
Interest income671 696 6 
Interest expense(16,806)(18,552)(2,202)
Income before income taxes$144 $162 $— 
Income Taxes(26)26 — 
Net Income$118 $188 $— 
v3.25.0.1
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
USD ($)
customers
Dec. 31, 2023
USD ($)
Dec. 31, 2022
USD ($)
Nov. 18, 2022
USD ($)
Significant Accounting Policies [Line Items]        
Number of natural gas distribution services customers | customers 2,300,000      
Segment Reporting, Disclosure of Major Customers no no no  
Allowance for Doubtful Accounts, Premiums and Other Receivables $ 14,900 $ 16,100    
Asset Impairment Charges 0 0 $ 0  
Finite-Lived Intangible Assets, Gross       $ 327,400
Finite-Lived Intangible Asset, Useful Life       10 years
Deferred Tax Assets, Valuation Allowance 0 0    
Liability for Uncertainty in Income Taxes, Current 0 0    
KGSS-I Amortization of Intangible Asset $ 27,700 $ 30,200    
v3.25.0.1
REVENUE (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Regulated Operating Revenue, Gas $ 2,045,872 $ 2,346,321 $ 2,561,618
Regulated Operating Revenue, Other 37,686 25,669 16,387
Regulated Operating Revenue 2,083,558 2,371,990 2,578,005
Unbilled Receivables, Current 212,000 191,400  
Natural gas sales to customers [Member]      
Regulated Operating Revenue, Gas 1,841,400 2,141,908 2,410,048
Transportation revenues [Member]      
Regulated Operating Revenue, Gas 137,111 132,945 125,951
Securitization Customer Charges      
Regulated Operating Revenue, Gas 44,390 48,677 5,769
Miscellaneous revenues [Member]      
Regulated Operating Revenue, Gas 22,971 22,791 19,850
Other revenues - natural gas sales related [Member]      
Regulated Operating Revenue, Other 24,296 12,764 3,403
Other revenues [Member]      
Regulated Operating Revenue, Other $ 13,390 $ 12,905 $ 12,984
v3.25.0.1
REGULATORY ASSETS AND LIABILITIES (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]      
Regulatory Assets, Current $ 101,210 $ 75,308  
Regulatory Assets, Noncurrent 278,006 287,906  
Regulatory Assets 379,216 363,214  
Regulatory Liability, Current (22,525) (66,901)  
Regulatory Liability, Noncurrent (467,563) (500,478)  
Regulatory Liabilities (490,088) (567,379)  
Net Regulatory Assets (Liabilities), Current 78,685 8,407  
Net Regulatory Assets (Liabilities), Noncurrent (189,557) (212,572)  
Net Regulatory Assets (Liabilities) (110,872) (204,165)  
Amortization of Rate Deferral 14,400 14,700 $ 9,400
Income tax rate changes [Member] [Domain]      
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]      
Regulatory Liability, Current 0 0  
Regulatory Liability, Noncurrent (467,563) (500,478)  
Regulatory Liabilities (467,563) (500,478)  
Over-recovered purchased-gas costs [Member]      
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]      
Regulatory Liability, Current (22,525) (66,901)  
Regulatory Liability, Noncurrent 0 0  
Regulatory Liabilities (22,525) (66,901)  
Winter weather event costs      
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]      
Regulatory Assets, Current 9,051 22,633  
Regulatory Assets, Noncurrent 15,938 21,495  
Regulatory Assets 24,989 44,128  
Under-recovered purchased-gas costs [Member]      
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]      
Regulatory Assets, Current 43,819 10,391  
Regulatory Assets, Noncurrent 0 0  
Regulatory Assets 43,819 10,391  
Pension and postretirement benefit costs [Member]      
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]      
Regulatory Assets, Current 1,358 6,379  
Regulatory Assets, Noncurrent 224,837 228,092  
Regulatory Assets 226,195 234,471  
Reacquired debt costs [Member]      
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]      
Regulatory Assets, Current 723 723  
Regulatory Assets, Noncurrent 1,989 2,712  
Regulatory Assets 2,712 3,435  
MGP Costs [Member] [Member]      
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]      
Regulatory Assets, Current 1,000 98  
Regulatory Assets, Noncurrent 30,067 31,893  
Regulatory Assets 31,067 31,991  
Ad valorem tax [Member]      
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]      
Regulatory Assets, Current 14,066 14,533  
Regulatory Assets, Noncurrent 0 0  
Regulatory Assets 14,066 14,533  
Weather normalization [Member]      
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]      
Regulatory Assets, Current 26,684 11,404  
Regulatory Assets, Noncurrent 0 0  
Regulatory Assets 26,684 11,404  
Customer credit deferrals      
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]      
Regulatory Assets, Current 255 6,184  
Regulatory Assets, Noncurrent 3,639 0  
Regulatory Assets 3,894 6,184  
Other regulatory assets [Member]      
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]      
Regulatory Assets, Current 4,254 2,963  
Regulatory Assets, Noncurrent 1,536 3,714  
Regulatory Assets $ 5,790 $ 6,677  
v3.25.0.1
CREDIT FACILITIES (Details) - USD ($)
 12 Months Ended
Dec. 31, 2024
Sep. 30, 2024
Jul. 25, 2024
Jun. 30, 2024
Jun. 26, 2024
Dec. 31, 2023
Short-term Debt [Line Items]            
Line of Credit Facility, Maximum Borrowing Capacity $ 1,350,000,000 $ 1,275,000,000   $ 1,275,000,000 $ 1,200,000,000  
Line of Credit Facility Sublimit 20,000,000          
Swingline subfacility 60,000,000          
Line of Credit Facility Option to Increase Borrowing Capacity $ 150,000,000          
Approved Debt to Capital Ratio 70.00%          
Ratio of Indebtedness to Net Capital 0.518          
Ratio of Indebtedness to Net Capital Excluding KGSS-I debt 49.50%          
Letters of Credit Outstanding, Amount $ 1,350,000          
Short-Term Debt 0          
Line of Credit Facility, Remaining Borrowing Capacity 1,349,000,000          
Commercial paper maximum borrowing capacity $ 1,350,000,000 $ 1,275,000,000 $ 1,275,000,000 $ 1,200,000,000    
CommercialPaperMaximumMaturityTerm 270 days          
Short-term debt $ 914,600,000         $ 88,500,000
Short-Term Debt, Weighted Average Interest Rate, at Point in Time 4.77%         5.60%
v3.25.0.1
LONG-TERM DEBT (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Jun. 30, 2024
Dec. 31, 2024
Dec. 31, 2023
Debt Instrument [Line Items]      
Long-Term Debt   $ 2,414,256 $ 2,960,815
Debt Instrument, Unamortized Discount   (3,624) (7,615)
Debt Issuance Costs, Net   (20,691) (21,092)
Long-term Debt, Current Maturities   14 772,984
Long-term Debt, excluding current maturities   2,385,286 2,160,401
Debt Instrument, Covenant Compliance, Default Provision, Indebtnedness Threshold   $ 100,000  
Debt Instrument, Covenant Compliance, Default Provision, Debt Holders   25.00%  
Debt Instrument, Redemption Price, Percentage   100.00%  
Kansas Gas Service Securitization I LLC      
Debt Instrument [Line Items]      
Debt Issuance Costs, Net   $ (4,800) (5,300)
3.61% Senior Unsecured Notes Due 2024      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 3.61% 3.61%  
Long-term Debt, Gross   $ 0 300,000
Repayments of Debt $ 300,000    
1.10% Senior Unsecured Notes Due 2024      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 1.10% 1.10%  
Long-term Debt, Gross   $ 0 473,000
Repayments of Debt $ 473,000    
5.10% Senior Unsecured Notes Due 2029 [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage   5.10%  
Long-term Debt, Gross   $ 550,000 300,000
Additional Long-term Debt, Gross   $ 250,000  
2.00% Senior Unsecured Notes Due 2024      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage   2.00%  
Long-term Debt, Gross   $ 300,000 300,000
4.25% Senior Unsecured Notes Due 2032      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage   4.25%  
Long-term Debt, Gross   $ 300,000 300,000
4.658% Senior Unsecured Notes Due 2044      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage   4.658%  
Long-term Debt, Gross   $ 600,000 600,000
4.50% Senior Unsecured Notes Due 2048      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage   4.50%  
Long-term Debt, Gross   $ 400,000 400,000
Total Senior Unsecured Notes      
Debt Instrument [Line Items]      
Long-term Debt, Gross   $ 2,150,000 2,673,000
5.486% KGSS-I Securitized Utility Tariff Bonds Due 2032      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage   5.486%  
Long-term Debt, Gross   $ 287,345 315,284
Long-term Debt, Current Maturities   $ 28,956 27,430
8.00% Other Long Term Debt      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage   8.00%  
Long-term Debt, Gross   $ 1,226 $ 1,238
v3.25.0.1
Leases (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Lessee, Lease, Description [Line Items]      
Lessee, Operating Lease, Option to Extend 10 years    
Operating Lease, Right-of-Use Asset $ 17.5 $ 21.0  
Operating Lease, Cost 7.7 $ 7.7 $ 7.8
Operating Lease, Right-of-Use Asset, Periodic Reduction $ 2.7    
Operating Lease, Weighted Average Remaining Lease Term 4 years 4 years 5 years
Operating Lease, Weighted Average Discount Rate, Percent 4.37% 4.28% 4.04%
Operating Lease, Payments $ 7.9 $ 8.3 $ 8.2
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability 2.7 $ 3.9 $ 0.3
Lessee, Operating Lease, Liability, to be Paid, Year One 5.9    
Lessee, Operating Lease, Liability, to be Paid, Year Two 4.3    
Lessee, Operating Lease, Liability, to be Paid, Year Three 3.3    
Lessee, Operating Lease, Liability, to be Paid, Year Four 3.0    
Lessee, Operating Lease, Liability, to be Paid, Rolling Year Five 1.5    
Operating Leases, Future Minimum Payments, Due Thereafter 0.0    
Lessee, Operating Lease, Liability, to be Paid 18.0    
Lessee, Operating Lease, Liability, Undiscounted Excess Amount 1.4    
Operating Lease, Liability 16.6    
Operating Lease, Liability, Current 5.2    
Operating Lease, Liability, Noncurrent $ 11.4    
Minimum [Member]      
Lessee, Lease, Description [Line Items]      
Lessee Operating Lease Minimum Term Of Contract less than one year    
Maximum [Member]      
Lessee, Lease, Description [Line Items]      
Lessee, Operating Lease, Term of Contract 5 years    
v3.25.0.1
EQUITY (Details) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 12 Months Ended
Mar. 07, 2025
Feb. 21, 2025
Dec. 27, 2024
Mar. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Preferred Stock, Shares Authorized         50,000,000     50,000,000    
Preferred Stock, Par or Stated Value Per Share         $ 0.01     $ 0.01    
Common Stock Authorized and Available for Issuance         190,100,000     190,100,000    
Forward Contract Indexed to Equity, Settlement, Number of Shares Issued     3,160,465              
At-The-Market Program Shares Issued     926,465              
Shares Issued From Forwards Related to Underwriting Agreements     2,234,000              
Proceeds from Issuance of Common Stock     $ 245,700         $ 252,379 $ 85,259 $ 133,711
Forward Contract Indexed to Equity, Settlement, Original Number of Shares         1,380,000     1,380,000    
Forward Contract Indexed to Issuer's Equity, Indexed Shares         403,000     403,000    
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share               $ 74.63    
Forward Contract Indexed to Equity, Settlement, Cash, Amount         $ 30,075     $ 30,075    
Dividends paid per share of stock               $ 2.64 $ 2.60 $ 2.48
us-gaap_CommonStockDividendsPerShareCashPaidQuaterly         $ 0.66 $ 0.65        
Common Stock, Dividends, Per Share, Declared               $ 2.64 $ 2.60 $ 2.48
At-The-Market Program                    
Proceeds from Issuance of Common Stock     75,200              
September 11, 2023 Equity Forward Agreement [Domain]                    
Forward Contract Indexed to Equity, Shares with Extended Maturity Date         223,000     223,000    
September 15, 2023 Equity Forward Agreement [Domain]                    
Forward Contract Indexed to Equity, Shares with Extended Maturity Date         180,000     180,000    
Forwards Related to Underwriting Agreements                    
Proceeds from Issuance of Common Stock     $ 170,500              
At-The-Market Program                    
Aggregate Offering Price Limit         $ 300,000     $ 300,000    
Equity Available for Issuance         $ 225,500     $ 225,500    
September 11, 2023 Equity Forward Agreement [Domain]                    
Forward Contract Indexed to Equity, Settlement, Original Number of Shares         1,200,000     1,200,000    
Forward Contract Indexed to Issuer's Equity, Indexed Shares         223,000     223,000    
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share               $ 74.65    
Forward Contract Indexed to Equity, Settlement, Cash, Amount         $ 16,647     $ 16,647    
September 15, 2023 Equity Forward Agreement [Domain]                    
Forward Contract Indexed to Equity, Settlement, Original Number of Shares         180,000     180,000    
Forward Contract Indexed to Issuer's Equity, Indexed Shares         180,000     180,000    
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share               $ 74.60    
Forward Contract Indexed to Equity, Settlement, Cash, Amount         $ 13,428     $ 13,428    
Subsequent Event [Member]                    
Common Stock, Dividends, Per Share, Declared       $ 0.67            
Common Stock, Dividends, Declared, Annualized Basis             $ 2.68      
Dividends Payable, Date of Record   Feb. 21, 2025                
Dividends Payable, Date to be Paid Mar. 07, 2025                  
v3.25.0.1
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Accumulated other comprehensive loss $ (126) $ (1,182) $ (704)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Before Reclassification Adjustment from AOCI, Tax (281) 140  
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, after Tax 961 (477)  
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax 0 0  
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax (1) (1)  
Other comprehensive income (loss) 1,056 (478) 5,823
OCI, Debt Securities, Available-for-Sale, Gain (Loss), before Adjustment, Tax (24)    
OCI, Debt Securities, Available-for-Sale, Gain (Loss), before Adjustment, after Tax 94    
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax (1)    
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax 2    
Defined benefit plan, amortization of net (gain) loss (5,770) (1,960) (17,010)
Defined benefit plan, amortization of unrecognized prior service cost 372 525 289
Defined benefit plan, reclassification adjustment, before tax and regulatory adjustments (6,142) (2,485) (17,299)
Defined benefit plan, regulatory adjustments (6,143) (2,486) (17,141)
Debt Securities, Available-for-Sale, Realized Gain (Loss) (3) 0 0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax (3) 0 0
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax (2) 1 (158)
Reclassification from AOCI, Current Period, Tax 1 0 36
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax (1) 1 (122)
ONE Gas Pension Plans [Member]      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Other Comprehensive (Income) Loss, Defined Benefit Plan, Before Reclassification Adjustment from AOCI, Tax (281) 140 (1,705)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax (1) 1 159
Defined benefit plan, amortization of net (gain) loss (5,786) (2,008) (16,793)
Defined benefit plan, amortization of unrecognized prior service cost (372) (372) (248)
Defined benefit plan, reclassification from AOCI, Current Period, before Tax, Attributable to Parent $ 1 $ 1 $ (158)
v3.25.0.1
EARNINGS PER SHARE (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Basic EPS Calculation      
Net income available for common stock $ 222,850 $ 231,232 $ 221,742
Weighted Average Number of Shares Outstanding, Basic 56,826 55,600 54,207
Earnings Per Share, Basic $ 3.92 $ 4.16 $ 4.09
Diluted EPS Calculation      
Net Income (Loss) Available to Common Stockholders, Diluted $ 222,850 $ 231,232 $ 221,742
Effect of dilutive securities on shares 207 260 131
Weighted Average Number of Shares Outstanding, Diluted 57,033 55,860 54,338
Earnings Per Share, Diluted $ 3.91 $ 4.14 $ 4.08
v3.25.0.1
Compensation Related Costs, Share Based Payments (Details) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]      
Common Stock, Capital Shares Reserved for Future Issuance 4,300,000    
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant 1,700,000    
Share-Based Payment Arrangement, Expense, after Tax $ 8,800 $ 7,800 $ 6,800
Share-Based Payment Arrangement, Expense, Tax Benefit $ 2,900 2,600 $ 2,300
Restricted Stock Units (RSUs)      
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period 3 years    
Forfeiture Rate Maximum In Hundredths 3.00%    
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount $ 4,200 $ 4,000  
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition 1 year 8 months 12 days    
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number 149,037 126,948  
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period 67,432    
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period (41,168)    
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Nonvested Options Forfeited, Number of Shares (4,175)    
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value $ 68.79 $ 77.50  
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value 60.74 $ 81.79 $ 76.96
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value 72.46    
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value $ 71.40    
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Fair Value Of Shares Granted $ 4,096 $ 3,995 $ 4,342
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Fair Value Of Shares Vested $ 3,200 2,800 $ 2,900
Performance Shares      
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period 3 years    
Forfeiture Rate Maximum In Hundredths 3.00%    
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount $ 10,000 $ 9,700  
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition 1 year 8 months 12 days    
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number 305,485 247,326  
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period 139,727    
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period 0    
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Nonvested Options Forfeited, Number of Shares (81,568)    
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value $ 86.00 $ 95.23  
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value 67.83 $ 105.74 $ 95.80
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value 0    
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value $ 82.85    
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Fair Value Of Shares Granted $ 9,478 $ 10,095 $ 8,360
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Fair Value Of Shares Vested $ 0 $ 3,700 $ 5,200
Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Volatility Rate 26.63% 29.20% 34.00%
Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Dividend Rate 4.35% 3.18% 3.22%
Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Risk Free Interest Rate 4.46% 4.37% 1.65%
Employee Stock      
Share-Based Payment Arrangement [Abstract]      
Common Stock, Capital Shares Reserved for Future Issuance 1,250,000    
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Maximum Allowable Percentage Of Annual Base Pay Withheld To Purchase Our Common Stock 10.00%    
Purchase Price Percentage Of Lower O fIts Grant Date Or Exercise Date Market Price In Hundredths 85.00%    
Percent of employees who participated in the Employee Stock Purchase Plan 44.00% 45.00% 42.00%
Shares sold under employee stock purchase plan 122,906 108,875 86,657
Share price of shares sold under Employee Stock Purchase Plan in dollars per share $ 53.98 $ 58.98 $ 65.21
Share-Based Payment Arrangement, Expense $ 1,500 $ 1,200 $ 1,100
v3.25.0.1
EMPLOYEE BENEFIT PLANS (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Apr. 30, 2022
Components of net periodic benefit cost:        
Minimumnumberofyearsofserviceforcertainemployeestobeeligibletoparticipateinsharedwelfareplansthatprovidepostretirementmedicalandlifeinsurancebenefits 5 years      
DefinedBenefitPlanAssumptionsUsedToDetermineBenefitObligationsRateofCompensationIncreaseMinimum 3.50% 3.50%    
DefinedBenefitPlanAssumptionsUsedToDetermineBenefitObligationsRateofCompensationIncreaseMinimum 4.30% 4.30%    
DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncreaseMinimum 3.50% 3.60% 3.10%  
DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncreaseMaximum 4.30% 5.00% 5.00%  
Defined Benefit Plan, Plan Assets, Expected Long-Term Rate-of-Return, Description We determine our discount rates annually. We estimate our discount rate based upon a comparison of the expected cash flows associated with our future payments under our defined benefit pension and other postemployment obligations to a hypothetical bond portfolio created using high-quality bonds that closely match expected cash flows. Bond portfolios are developed by selecting a bond for each of the next 60 years based on the maturity dates of the bonds. Bonds selected to be included in the portfolios are only those rated by Moody’s as AA- or better and exclude callable bonds, bonds with less than a minimum issue size, yield outliers and other filtering criteria to remove unsuitable bonds.      
Regulatory Liability, Noncurrent $ 467,563 $ 500,478    
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) 27,000 23,000    
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position 42,882 36,482    
Defined Benefit Plan, Benefit Obligation, Payment for Settlement 39,000      
Defined benefit plan, amortization of unrecognized prior service cost (372) (525) $ (289)  
Defined benefit plan, amortization of net (gain) loss 5,770 1,960 17,010  
AdjustmentToPensionExpenseDueToRemeasurement       $ 7,200
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax (1) (1)    
Other Comprehensive (Income) Loss, Defined Benefit Plan, Before Reclassification Adjustment from AOCI, Tax (281) 140    
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax 960 (478) 5,823  
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax 0 0 0  
Regulatory Assets $ 379,216 $ 363,214    
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year 7.00% 6.00%    
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate 4.50% 4.50%    
Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate 2035 2030    
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 100.00%      
Defined Contribution Plan, Employer Discretionary Contribution Amount $ 10,900 $ 12,600 $ 10,900  
Cash Surrender Value of Life Insurance 41,500 37,900    
Nonservice Costs Member        
Components of net periodic benefit cost:        
Regulatory Liability, Noncurrent 6,700 2,200    
Grosvenor Registered Multi Limited Partnership        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 29,642 40,872    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments $ 0 $ 0    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency quarterly quarterly    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Description 65 65    
K2 Institutional Investors I I Limited Partnership        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount $ 30,028 $ 48,254    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments $ 0 $ 0    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency quarterly quarterly    
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Description 91 91    
Investment grade bonds        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 70.00%      
US Large Cap Equity        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 13.00%      
Alternative Investments        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 7.00%      
Developed Foreign Equities        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 5.00%      
Mid Cap Equities        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 3.00%      
Emerging Market Equities        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 1.00%      
Small Cap Equities        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 1.00%      
Fixed Income Funds        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description 90 percent      
Equity Securities        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description 10 percent      
ONE Gas Pension Plans [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate 5.70% 5.30%    
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate 5.30% 5.60% 3.05%  
DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRateAfterRemeasurement     4.55%  
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-Term Rate of Return on Plan Assets 6.70% 6.75% 6.40%  
Defined Benefit Plan, Benefit Obligation $ 731,117 $ 803,605 $ 784,633  
Service cost 6,204 7,242 10,369  
Interest cost 41,123 42,428 36,150  
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant 0 0    
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) (27,026) 23,015    
Defined Benefit Plan, Benefit Obligation, Benefits Paid (54,099) (53,713)    
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement (38,690) 0    
Defined Benefit Plan, Plan Assets, Amount 725,401 795,381 768,961  
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss) 22,322 78,827    
Defined Benefit Plan, Plan Assets, Contributions by Employer 1,559 1,306    
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant 0 0    
Defined Benefit Plan, Plan Assets, Benefits Paid (54,099) (53,713)    
Defined Benefit Plan, Plan Assets, Payment for Settlement (39,762) 0    
Defined Benefit Plan, Funded (Unfunded) Status of Plan (5,716) (8,224)    
Assets for Plan Benefits, Defined Benefit Plan 14,377 13,409    
Liability, Defined Benefit Plan, Current (1,409) (1,368)    
Employee benefit obligations (18,684) (20,265)    
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position (5,716) (8,224)    
Defined Benefit Plan, Accumulated Benefit Obligation 703,400 772,100    
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year 9,800      
Expected return on assets (59,027) (59,518) (58,528)  
Defined benefit plan, amortization of unrecognized prior service cost 372 372 248  
Defined benefit plan, amortization of net (gain) loss 5,786 2,008 16,793  
Net periodic benefit cost (5,542) (7,468) 5,032  
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, after Tax 1,242 (619) 7,369  
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax (1) 1 159  
Other Comprehensive (Income) Loss, Defined Benefit Plan, Before Reclassification Adjustment from AOCI, Tax (281) 140 (1,705)  
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax (1,720) (2,091)    
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax (251,952) (246,988)    
DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeLossBeforeRegulatoryAssetsAndTaxes (253,672) (249,079)    
Regulatory Assets 253,517 247,684    
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax (155) (1,395)    
Deferred Tax Liabilities, Regulatory Assets (67) 213    
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax (222) (1,182)    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value 70,847 101,476 101,511  
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase 445 2,095    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period (Decrease) (2,984) (618)    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Expense (167)      
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases 1,408 1,562    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales (27,880)      
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements (1,451) (3,074)    
Defined Benefit Plan, Benefits Paid 54,100      
Defined Benefit Plan, Expected Future Benefit Payment, Year One 52,832      
Defined Benefit Plan, Expected Future Benefit Payment, Year Two 53,298      
Defined Benefit Plan, Expected Future Benefit Payment, Year Three 53,470      
Defined Benefit Plan, Expected Future Benefit Payment, Year Four 54,189      
Defined Benefit Plan, Expected Future Benefit Payment, Year Five 54,094      
Defined Benefit Plan, Expected Future Benefit Payment, after Year Five for Next Five Years 271,532      
ONE Gas Pension Plans [Member] | Fair Value, Inputs, Level 1 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 87,330 93,777    
ONE Gas Pension Plans [Member] | Fair Value, Inputs, Level 2 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 567,224 600,128    
ONE Gas Pension Plans [Member] | Fair Value, Inputs, Level 3        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 70,847 101,476    
ONE Gas Pension Plans [Member] | Equity Securities        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 81,459 88,477    
ONE Gas Pension Plans [Member] | Equity Securities | Fair Value, Inputs, Level 1 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 81,459 88,477    
ONE Gas Pension Plans [Member] | Equity Securities | Fair Value, Inputs, Level 2 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Pension Plans [Member] | Equity Securities | Fair Value, Inputs, Level 3        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Pension Plans [Member] | Government Obligations        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 213,572 204,669    
ONE Gas Pension Plans [Member] | Government Obligations | Fair Value, Inputs, Level 1 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Pension Plans [Member] | Government Obligations | Fair Value, Inputs, Level 2 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 213,572 204,669    
ONE Gas Pension Plans [Member] | Government Obligations | Fair Value, Inputs, Level 3        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Pension Plans [Member] | Corporate Obligations        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 328,915 366,482    
ONE Gas Pension Plans [Member] | Corporate Obligations | Fair Value, Inputs, Level 1 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Pension Plans [Member] | Corporate Obligations | Fair Value, Inputs, Level 2 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 328,915 366,482    
ONE Gas Pension Plans [Member] | Corporate Obligations | Fair Value, Inputs, Level 3        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Pension Plans [Member] | Cash and Money Market Funds        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 30,608 34,277    
ONE Gas Pension Plans [Member] | Cash and Money Market Funds | Fair Value, Inputs, Level 1 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 5,871 5,300    
ONE Gas Pension Plans [Member] | Cash and Money Market Funds | Fair Value, Inputs, Level 2 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 24,737 28,977    
ONE Gas Pension Plans [Member] | Cash and Money Market Funds | Fair Value, Inputs, Level 3        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Pension Plans [Member] | Insurance Contracts and Group Annuity Contracts        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 11,177 12,350    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value 11,177 12,350 14,480  
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase 445 0    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period (Decrease) 0 (618)    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Expense (167)      
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases 0 1,562    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales 0      
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements (1,451) (3,074)    
ONE Gas Pension Plans [Member] | Insurance Contracts and Group Annuity Contracts | Fair Value, Inputs, Level 1 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Pension Plans [Member] | Insurance Contracts and Group Annuity Contracts | Fair Value, Inputs, Level 2 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Pension Plans [Member] | Insurance Contracts and Group Annuity Contracts | Fair Value, Inputs, Level 3        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 11,177 12,350    
ONE Gas Pension Plans [Member] | Other Investments        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 59,670 89,126    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value 59,670 89,126 $ 87,031  
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase 0 2,095    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period (Decrease) (2,984) 0    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Expense 0      
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases 1,408 0    
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales (27,880)      
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements 0 0    
ONE Gas Pension Plans [Member] | Other Investments | Fair Value, Inputs, Level 1 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Pension Plans [Member] | Other Investments | Fair Value, Inputs, Level 2 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Pension Plans [Member] | Other Investments | Fair Value, Inputs, Level 3        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount $ 59,670 $ 89,126    
ONE Gas Postretirement Benefit Plans [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate 5.75% 5.40%    
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate 5.40% 5.70% 3.00%  
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-Term Rate of Return on Plan Assets 5.20% 5.55% 5.85%  
Defined Benefit Plan, Benefit Obligation $ 150,984 $ 158,535 $ 168,342  
Service cost 610 730 1,274  
Interest cost 8,179 9,154 6,448  
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant 2,631 2,823    
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) (3,267) (5,551)    
Defined Benefit Plan, Benefit Obligation, Benefits Paid (15,704) (16,963)    
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement 0 0    
Defined Benefit Plan, Plan Assets, Amount 179,489 181,608 181,877  
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss) 8,404 11,325    
Defined Benefit Plan, Plan Assets, Contributions by Employer 0 2,546    
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant 2,631 2,823    
Defined Benefit Plan, Plan Assets, Benefits Paid (13,154) (16,963)    
Defined Benefit Plan, Plan Assets, Payment for Settlement 0 0    
Defined Benefit Plan, Funded (Unfunded) Status of Plan 28,505 23,073    
Assets for Plan Benefits, Defined Benefit Plan 28,505 23,073    
Liability, Defined Benefit Plan, Current 0 0    
Employee benefit obligations 0 0    
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position 28,505 23,073    
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year 0      
Expected return on assets (9,134) (9,728) (13,181)  
Defined benefit plan, amortization of unrecognized prior service cost 0 153 41  
Defined benefit plan, amortization of net (gain) loss (16) (48) 217  
Net periodic benefit cost (361) 261 (5,201)  
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax 0 0    
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax 1,065 (1,457)    
DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeLossBeforeRegulatoryAssetsAndTaxes 1,065 (1,457)    
Regulatory Assets (1,065) 1,457    
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax 0 0    
Defined Benefit Plan, Benefits Paid 15,700      
Defined Benefit Plan, Expected Future Benefit Payment, Year One 14,127      
Defined Benefit Plan, Expected Future Benefit Payment, Year Two 13,734      
Defined Benefit Plan, Expected Future Benefit Payment, Year Three 13,431      
Defined Benefit Plan, Expected Future Benefit Payment, Year Four 13,069      
Defined Benefit Plan, Expected Future Benefit Payment, Year Five 12,745      
Defined Benefit Plan, Expected Future Benefit Payment, after Year Five for Next Five Years 58,985      
ONE Gas Postretirement Benefit Plans [Member] | Fair Value, Inputs, Level 1 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 8,032 7,782    
ONE Gas Postretirement Benefit Plans [Member] | Fair Value, Inputs, Level 2 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 171,457 173,825    
ONE Gas Postretirement Benefit Plans [Member] | Fair Value, Inputs, Level 3        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Postretirement Benefit Plans [Member] | Equity Securities        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 7,226 7,031    
ONE Gas Postretirement Benefit Plans [Member] | Equity Securities | Fair Value, Inputs, Level 1 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 7,226 7,031    
ONE Gas Postretirement Benefit Plans [Member] | Equity Securities | Fair Value, Inputs, Level 2 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Postretirement Benefit Plans [Member] | Equity Securities | Fair Value, Inputs, Level 3        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Postretirement Benefit Plans [Member] | Government Obligations        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 41,982 41,863    
ONE Gas Postretirement Benefit Plans [Member] | Government Obligations | Fair Value, Inputs, Level 1 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Postretirement Benefit Plans [Member] | Government Obligations | Fair Value, Inputs, Level 2 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 41,982 41,863    
ONE Gas Postretirement Benefit Plans [Member] | Government Obligations | Fair Value, Inputs, Level 3        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Postretirement Benefit Plans [Member] | Corporate Obligations        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 36,411 38,615    
ONE Gas Postretirement Benefit Plans [Member] | Corporate Obligations | Fair Value, Inputs, Level 1 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Postretirement Benefit Plans [Member] | Corporate Obligations | Fair Value, Inputs, Level 2 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 36,411 38,615    
ONE Gas Postretirement Benefit Plans [Member] | Corporate Obligations | Fair Value, Inputs, Level 3        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Postretirement Benefit Plans [Member] | Cash and Money Market Funds        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 12,973 13,996    
ONE Gas Postretirement Benefit Plans [Member] | Cash and Money Market Funds | Fair Value, Inputs, Level 1 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 806 751    
ONE Gas Postretirement Benefit Plans [Member] | Cash and Money Market Funds | Fair Value, Inputs, Level 2 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 12,167 13,245    
ONE Gas Postretirement Benefit Plans [Member] | Cash and Money Market Funds | Fair Value, Inputs, Level 3        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Postretirement Benefit Plans [Member] | Insurance Contracts and Group Annuity Contracts        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 80,897 80,102    
ONE Gas Postretirement Benefit Plans [Member] | Insurance Contracts and Group Annuity Contracts | Fair Value, Inputs, Level 1 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 0 0    
ONE Gas Postretirement Benefit Plans [Member] | Insurance Contracts and Group Annuity Contracts | Fair Value, Inputs, Level 2 [Member]        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount 80,897 80,102    
ONE Gas Postretirement Benefit Plans [Member] | Insurance Contracts and Group Annuity Contracts | Fair Value, Inputs, Level 3        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount $ 0 0    
ONE Gas Postretirement Benefit Plans [Member] | Other Investments        
Components of net periodic benefit cost:        
Defined Benefit Plan, Plan Assets, Amount   181,607    
401k Plan        
Components of net periodic benefit cost:        
Defined Contribution Plan, Employer Matching Contribution, Percent of Match 100.00%      
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay 6.00%      
Defined Contribution Plan, Cost $ 17,700 16,700 15,300  
Nonqualified Plan        
Components of net periodic benefit cost:        
Other Deferred Compensation Arrangements, Liability, Current and Noncurrent 18,900 16,000    
Deferred Compensation Arrangement with Individual, Compensation Expense $ 2,400 $ 2,300 $ (2,300)  
v3.25.0.1
INCOME TAXES (Details) - USD ($)
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Mar. 31, 2025
Income Tax Disclosure [Abstract]        
Current Federal Tax Expense (Benefit) $ (68,660,000) $ 16,551,000 $ 61,745,000  
Current State and Local Tax Expense (Benefit) (1,476,000) (829,000) 6,815,000  
Income Tax Expense (Benefit) (70,136,000) 15,722,000 68,560,000  
Deferred Federal Income Tax Expense (Benefit) 110,717,000 21,905,000 (22,234,000)  
Deferred State and Local Income Tax Expense (Benefit) (4,195,000) 2,868,000 200,000  
Deferred Income Taxes and Tax Credits 106,522,000 24,773,000 (22,034,000)  
Income Tax Expense (Benefit) 36,386,000 40,495,000 46,526,000  
Reduction in income tax expense for the amortization of the regulatory liability associated with excess ADIT that was returned to customers 25,700,000 22,400,000    
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Benefits 0 0    
Deferred Tax Assets, Regulatory adjustments 100,718,000 107,948,000    
Deferred Tax Assets, Operating Loss Carryforwards 405,316,000 93,255,000    
Deferred Tax Assets, Leasing Arrangements 3,669,000 4,500,000    
Deferred Tax Assets, Regulatory Assets - purchased-gas cost adjustment 0 5,232,000    
Deferred Tax Assets, Other 0 0    
Deferred Tax Assets, Gross 509,703,000 210,935,000    
Deferred Tax Liabilities, Property, Plant and Equipment 930,680,000 822,619,000    
Deferred Tax Liabilities, Winter weather events 381,818,000 56,914,000    
Deferred Tax Liabilities, Regulatory Liabilities - purchased-gas cost adjustment 8,654,000 0    
Deferred Tax Liabilities, Regulatory Assets and Liabilities - other 73,904,000 70,384,000    
Deferred Tax Liabilities, Tax Deferred Expense, Compensation and Benefits 934,000 205,000    
Deferred Tax Liabilities, Leasing Arrangements 3,866,000 4,662,000    
Deferred Tax Liabilities, Other 1,585,000 8,219,000    
Deferred Tax Liabilities, Gross 1,401,441,000 963,003,000    
Deferred income taxes 891,738,000 752,068,000    
ONGProceedsFromSecuritizationBonds     1,300,000,000  
Requested refund from 2022 amended federal tax return 55,500,000      
Effective Income Tax Rate Reconciliation [Line Items]        
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest $ 259,236,000 $ 271,727,000 $ 268,268,000  
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent 21.00% 21.00% 21.00%  
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount $ 54,439,000 $ 57,063,000 $ 56,335,000  
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount $ 4,333,000 $ 3,834,000 $ 7,016,000  
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent 2.00% 1.00% 3.00%  
Tax effect of permanent differences $ 2,018,000 $ 1,860,000 $ 1,369,000  
Tax effect of permanent differences, Percent 0.01 0.01 0.01  
Tax effect of state income tax deduction (209,000) (443,000) (1,254,000)  
Tax effect of state income tax deduction, Percent 0 0 0  
Amortization of EDIT Regulatory Liability (15,680,000) (20,565,000) (17,986,000)  
Amortization of EDIT Regulatory Liability, Percent (0.06) (0.08) (0.07)  
Amortization of EDIT Regulatory Liability - State Tax (10,004,000) (1,795,000) 0  
Amortization of EDIT Regulatory Liability - State Tax, Percent (0.04) (0.01) 0  
Effective Income Tax Rate Reconciliation, Tax Expense (Benefit), Share-Based Payment Arrangement, Amount $ 1,063,000 $ 418,000 $ 350,000  
Effective Income Tax Rate Reconciliation, Tax Expense (Benefit), Share-Based Payment Arrangement, Percent 0.00% 0.00% 0.00%  
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount $ 426,000 $ 123,000 $ 696,000  
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent 0.00% 0.00% 0.00%  
Effective Income Tax Rate Reconciliation, Percent 14.00% 14.00% 18.00%  
Operating Loss Carryforwards [Line Items]        
Deferred Tax Assets, Operating Loss Carryforwards $ 405,316,000 $ 93,255,000    
Subsequent Event [Member]        
Subsequent Event [Line Items]        
Future requested refund from amended Oklahoma corporate income tax return       $ 1,500,000
Domestic Tax Jurisdiction        
Income Tax Disclosure [Abstract]        
Deferred Tax Assets, Operating Loss Carryforwards 378,900,000      
Operating Loss Carryforwards [Line Items]        
Deferred Tax Assets, Operating Loss Carryforwards 378,900,000      
State and Local Jurisdiction        
Income Tax Disclosure [Abstract]        
Deferred Tax Assets, Operating Loss Carryforwards 26,400,000      
Operating Loss Carryforwards [Line Items]        
Deferred Tax Assets, Operating Loss Carryforwards $ 26,400,000      
v3.25.0.1
OTHER INCOME AND OTHER EXPENSE (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Other Nonoperating Income (Expense) $ 7,427 $ 9,476 $ (4,183)
Net periodic credit (cost) other than service cost      
Other Nonoperating Income (Expense) 3,600 4,017 3,766
Gain (loss) on investments associated with nonqualified deferred compensation plans      
Other Nonoperating Income (Expense) 3,653 4,826 (7,197)
Other, net      
Other Nonoperating Income (Expense) $ 174 $ 633 $ (752)
v3.25.0.1
Property, Plant, and Equipment (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Property, Plant and Equipment [Line Items]      
Property, Plant and Equipment, Other, Net $ 6,645,873 $ 6,135,212  
Property, plant and equipment 9,124,134 8,468,967  
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation $ (2,478,261) (2,333,755)  
Minimum [Member]      
Property, Plant and Equipment [Line Items]      
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service 2.70%    
Maximum [Member]      
Property, Plant and Equipment [Line Items]      
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service 3.20%    
Regulated Operation      
Property, Plant and Equipment [Abstract]      
Interest Costs Capitalized $ 8,200 5,700 $ 4,500
Property, Plant and Equipment [Line Items]      
Interest Costs Capitalized 8,200 5,700 4,500
Construction in Progress Expenditures Incurred but Not yet Paid 33,700 36,200 $ 28,600
Property, plant and equipment   8,468,967  
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation (2,478,261) (2,333,755)  
Regulated Operation | Gas Distribution Equipment      
Property, Plant and Equipment [Line Items]      
Property, plant and equipment 7,278,542 6,716,074  
Regulated Operation | Gas Transmission Equipment      
Property, Plant and Equipment [Line Items]      
Property, plant and equipment 736,229 713,505  
Regulated Operation | Land, Buildings and Improvements      
Property, Plant and Equipment [Line Items]      
Property, plant and equipment 942,677 907,946  
Regulated Operation | Construction in Progress      
Property, Plant and Equipment [Line Items]      
Property, plant and equipment $ 166,686 $ 131,442  
v3.25.0.1
COMMITMENTS AND CONTINGENCIES (Details)
$ in Thousands
 3 Months Ended
Jun. 30, 2024
USD ($)
Jan. 03, 2025
USD ($)
Dec. 31, 2024
USD ($)
Dec. 31, 2023
USD ($)
Commitments and Contingencies [Line Items]        
Number Of Former Manufactured Gas Sites Where We Own Or Retain Legal Responsibility For Environmental Conditions     12  
Number of sites with ongoing groundwater monitoring     7  
Number of sites where regulatory closure has been achieved     5  
Deferred MGP Costs, Maximum     $ 15,000  
Insurance proceeds related to MGP sites $ 1,700      
Regulatory Asset for Costs Associated with Manufactured Gas Sites     31,100 $ 32,000
Accrual for Environmental Loss Contingencies     $ 14,300  
Subsequent Event [Member]        
Commitments and Contingencies [Line Items]        
Deferred MGP Costs, Requested Increase   $ 32,000    
v3.25.0.1
DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Details) Note
$ in Thousands
 12 Months Ended
Dec. 31, 2024
USD ($)
Bcf
Dec. 31, 2023
USD ($)
Bcf
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Fair Value Assets, Transfers between Levels $ 0 $ 0
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement 21,892 17,576
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset (25)  
Long-term Debt, Fair Value $ 2,200,000 $ 2,800,000
Swap    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Derivative, Nonmonetary Notional Amount | Bcf 6.20 5.1
Commodity Option    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Derivative, Nonmonetary Notional Amount | Bcf 0.60 0.5
Premiums recorded in other current assets on natural gas contracts held $ 600 $ 500
Other Current Assets | Swap    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement 0  
Other Assets | US Treasury Securities    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement 8,721 6,496
Other Assets | Corporate Bond Securities    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement 13,171 11,080
Other Current Liabilities | Swap    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Financial Instruments, Owned, at Fair Value 3,213 13,920
Fair Value, Inputs, Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement 8,721 6,496
Fair Value, Inputs, Level 1 [Member] | Other Current Assets | Swap    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement 0  
Fair Value, Inputs, Level 1 [Member] | Other Assets | US Treasury Securities    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement 8,721 6,496
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset 0  
Fair Value, Inputs, Level 1 [Member] | Other Assets | Corporate Bond Securities    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement 0 0
Fair Value, Inputs, Level 1 [Member] | Other Current Liabilities | Swap    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Financial Instruments, Owned, at Fair Value 0 0
Fair Value, Inputs, Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement 13,196 11,080
Fair Value, Inputs, Level 2 [Member] | Other Current Assets | Swap    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement 25  
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset (25)  
Fair Value, Inputs, Level 2 [Member] | Other Assets | US Treasury Securities    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement 0 0
Fair Value, Inputs, Level 2 [Member] | Other Assets | Corporate Bond Securities    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement 13,171 11,080
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset 0  
Fair Value, Inputs, Level 2 [Member] | Other Current Liabilities | Swap    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Financial Instruments, Owned, at Fair Value 3,238 $ 13,920
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset $ (25)  
v3.25.0.1
VARIABLE INTEREST ENTITES (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Variable Interest Entity [Line Items]        
Restricted Cash and Cash Equivalents $ 20,542 $ 20,552    
Accounts receivable, net 408,448 347,864    
Assets 8,425,571 7,770,994    
Current maturities of securitized utility tariff bonds 28,956 27,430    
Accounts payable 261,321 278,056    
Discounts and issuance costs for securitized utility tariff bonds, excluding current maturities 4,800 5,300    
Stockholders' Equity Attributable to Parent 3,104,548 2,765,877 $ 2,584,426 $ 2,349,532
Liabilities and Equity 8,425,571 7,770,994    
Kansas Gas Service Securitization I LLC        
Variable Interest Entity [Line Items]        
Restricted Cash and Cash Equivalents 20,542 20,552    
Accounts receivable, net 4,659 5,133    
Finite-Lived Intangible Assets, Net 265,951 293,619    
Assets 291,152 319,304    
Current maturities of securitized utility tariff bonds 28,956 27,430    
Accounts payable 319 393    
Interest Payable 6,568 7,207    
Securitized utility tariff bonds 253,568 282,506    
Stockholders' Equity Attributable to Parent 1,741 1,768    
Liabilities and Equity 291,152 319,304    
Revenues 44,390 48,677 5,769  
Utilities Operating Expense (443) (440) (52)  
Depreciation and amortization (27,668) (30,219) (3,521)  
Interest Income 671 696 6  
Interest Expense (16,806) (18,552) (2,202)  
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest 144 162 0  
Variable Interest Entity, Measure of Activity, Income Tax (26) 26 0  
Variable Interest Entity, Measure of Activity, Net Income 118 $ 188 $ 0  
Finite-Lived Intangible Asset, Expected Amortization, Year One 29,102      
Finite-Lived Intangible Asset, Expected Amortization, Year Two 30,736      
Finite-Lived Intangible Asset, Expected Amortization, Year Three 32,462      
Finite-Lived Intangible Asset, Expected Amortization, Year Four 34,283      
Finite-Lived Intangible Asset, Expected Amortization, Year Five 36,206      
Finite-Lived Intangible Asset, Expected Amortization, after Year Five $ 103,162