NISOURCE INC., 10-Q filed on 8/5/2026
Quarterly Report
v3.26.1
Document And Entity Information - shares
 6 Months Ended
Jun. 30, 2026
Jul. 29, 2026
Document Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2026  
Document Transition Report false  
Entity File Number 001-16189  
Entity Registrant Name NiSource Inc.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 35-2108964  
Entity Address, Address Line One 801 East 86th Avenue  
Entity Address, City or Town Merrillville,  
Entity Address, State or Province IN  
Entity Address, Postal Zip Code 46410  
City Area Code (614)  
Local Phone Number 460-6000  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Emerging Growth Company false  
Entity Small Business false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   479,560,100
Entity Central Index Key 0001111711  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q2  
Amendment Flag false  
Common Stock    
Document Information [Line Items]    
Title of 12(b) Security Common Stock, par value $0.01 per share  
Trading Symbol NI  
Security Exchange Name NYSE  
v3.26.1
Statements of Consolidated Income (Loss) - USD ($)
shares in Millions, $ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Operating Revenues        
Customer revenues $ 1,289.5 $ 1,246.5 $ 3,611.8 $ 3,396.0
Other revenues 52.9 36.5 93.7 70.2
Total Operating Revenues 1,342.4 1,283.0 3,705.5 3,466.2
Loss on sale of assets 0.0 0.8 0.0 0.8
Operating Expenses        
Cost of energy 193.6 261.8 862.8 909.3
Operation and maintenance 474.9 396.2 964.1 824.0
Depreciation and amortization 362.2 286.7 650.5 545.3
Loss on impairment of assets 0.0 0.4 0.0 0.7
Other taxes 83.6 74.2 180.8 163.8
Operating Costs and Expenses 1,114.3 1,020.1 2,658.2 2,443.9
Operating Income 228.1 262.9 1,047.3 1,022.3
Other Income (Deductions)        
Interest expense, net (199.2) (139.1) (390.8) (271.9)
Other, net 18.2 0.5 32.6 6.3
Total Other Deductions, Net (181.0) (138.6) (358.2) (265.6)
Income before Income Taxes 47.1 124.3 689.1 756.7
Income Taxes 10.2 23.8 96.0 129.5
Net Income 36.9 100.5 593.1 627.2
Net income (loss) attributable to noncontrolling interest (8.6) (1.7) 40.5 50.2
Net Income Attributable to NiSource 45.5 102.2 552.6 577.0
Preferred dividends redemption premium reversal 0.0 0.0 3.6 0.0
Net Income Available to Common Shareholders $ 45.5 $ 102.2 $ 556.2 $ 577.0
Earnings Per Share        
Basic Earnings Per Share $ 0.10 $ 0.22 $ 1.16 $ 1.22
Diluted Earnings Per Share $ 0.09 $ 0.22 $ 1.15 $ 1.22
Basic Average Common Shares Outstanding 479.7 471.0 479.4 470.6
Diluted Average Common Shares 481.2 472.1 481.0 472.3
Noncontrolling Interest        
Other Income (Deductions)        
Net income (loss) attributable to noncontrolling interest $ (8.6) $ (1.7) $ 40.5 $ 50.2
v3.26.1
Statements of Consolidated Comprehensive Income (Loss) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Net Income $ 36.9 $ 100.5 $ 593.1 $ 627.2
Other comprehensive (loss) income:        
Net unrealized loss on available-for-sale securities [1] 0.7 1.0 (0.5) 1.8
Net unrealized gain (loss) on cash flow hedges (0.1) (0.1) (0.2) (0.2)
Unrecognized pension and OPEB benefit (costs) [2] (0.9) 0.1 (2.6) 0.6
Total other comprehensive (loss) income (0.3) 1.0 (3.3) 2.2
Comprehensive Income $ 36.6 $ 101.5 $ 589.8 $ 629.4
[1] Net unrealized (loss) gain on available-for-sale debt securities, net of zero tax benefit and $0.3 million tax expense in the second quarter of 2026 and 2025, respectively, and $0.3 million of tax benefit and $0.5 million of tax expense for the six months ended 2026 and 2025, respectively.
(2)Reclassification adjustment for cash flow hedges, net of $0.1 million tax benefit in the second quarter and six months ended 2026 and 2025, respectively.
[2] Unrecognized pension and OPEB benefit (cost), net of $0.1 million tax benefit and $0.1 million tax expense in the second quarter of 2026 and 2025, respectively, and $1.4 million of tax expense and $0.2 million of tax expense for the six months ended 2026 and 2025, respectively.
v3.26.1
Statements of Consolidated Comprehensive Income (Loss) (Parenthetical) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax     $ 0.1  
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax $ 0.0 $ (0.3) 0.3 $ (0.5)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax $ 0.1 $ (0.1) $ (1.4) $ (0.2)
v3.26.1
Statements of Consolidated Balance Sheets - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Property, Plant and Equipment    
Plant $ 40,300.8 $ 38,058.8
Accumulated depreciation and amortization (9,779.5) (9,370.6)
Net Property, Plant and Equipment [1] 30,521.3 28,688.2
Investments and Other Assets    
Unconsolidated affiliates 8.2 8.1
Available-for-sale debt securities (amortized cost of $164.6 and $145.8, respectively) 163.3 146.1
Other investments 121.5 118.6
Total Investments and Other Assets 293.0 272.8
Current Assets    
Cash and cash equivalents 70.0 110.1
Restricted Cash 25.4 25.6
Accounts receivable 886.7 1,238.1
Allowance for credit losses (40.2) (40.6)
Accounts receivable, net 846.5 1,197.5
Gas storage 173.6 252.0
Materials and supplies, at average cost 212.4 189.0
Electric production fuel, at average cost 22.4 8.5
Exchange gas receivable 37.9 66.0
Regulatory assets 400.0 274.2
Income Taxes Receivable 7.6 15.7
Prepayments and other 157.5 89.3
Total Current Assets [1] 2,199.4 2,377.2
Other Assets    
Regulatory assets 2,360.8 2,225.2
Goodwill 1,485.9 1,485.9
Deferred charges and other 683.2 809.4
Total Other Assets 4,529.9 4,520.5
Total Assets 37,543.6 35,858.7
Stockholders' Equity    
Common stock - $0.01 par value,750,000,000 shares authorized; 479,498,053 and 478,432,058 shares outstanding, respectively 4.8 4.8
Treasury stock (99.9) (99.9)
Additional paid-in capital 9,875.4 9,866.6
Retained deficit (196.2) (315.2)
Accumulated other comprehensive loss (9.5) (6.2)
Total NiSource Stockholders’ Equity 9,574.6 9,450.1
Noncontrolling interest in consolidated subsidiaries 2,319.8 2,209.8
Total Stockholders’ Equity 11,894.4 11,659.9
Long-term debt, excluding amounts due within one year 15,612.6 15,457.8
Total Capitalization 27,507.0 27,117.7
Current Liabilities    
Current portion of long-term debt 1,098.4 19.7
Short-term borrowings 692.0 736.0
Accounts payable 1,135.6 1,124.5
Dividends payable - common stock 148.0 4.4
Customer deposits and credits 163.8 283.4
Taxes accrued 246.3 228.8
Interest accrued 241.4 206.2
Exchange gas payable 76.8 125.4
Regulatory liabilities 188.1 260.1
Asset Retirement Obligation 48.1 55.0
Accrued compensation and employee benefits 190.7 246.8
Other accruals 185.3 167.1
Total Current Liabilities [2] 4,414.5 3,457.4
Other Liabilities    
Deferred income taxes 2,623.8 2,500.1
Accrued liability for postretirement and postemployment benefits 140.1 153.1
Regulatory liabilities 1,586.2 1,513.3
Asset retirement obligations 811.8 781.9
Other noncurrent liabilities 381.5 258.0
Total Other Liabilities [2] 5,622.1 5,283.6
Total Capitalization and Liabilities $ 37,543.6 $ 35,858.7
Common Stock, Shares Authorized 750,000,000 750,000,000
Common Stock, No Par Value $ 0.01 $ 0.01
Prepaid Expense, Current $ 246.1 $ 149.3
Accrued insurance liabilities 78.7 77.2
Variable Interest Entity Primary Beneficiary Member GenCo    
Other Liabilities    
Other Assets 210.7 305.4
Joint Ventures    
Property, Plant and Equipment    
Net Property, Plant and Equipment 1,764.0 1,312.7
Current Assets    
Total Current Assets 223.4 90.1
Current Liabilities    
Total Current Liabilities 335.6 56.9
Other Liabilities    
Total Other Liabilities $ 57.0 $ 55.7
[1] Includes $1,764.0 million and $1,312.7 million at June 30, 2026 and December 31, 2025, respectively, of net property, plant and equipment assets and $223.4 million and $90.1 million at June 30, 2026 and December 31, 2025, respectively, of current assets of consolidated VIEs that may be used only to settle obligations of the consolidated VIEs. Refer to Note 4, "Noncontrolling Interests," for additional information.
(2)Includes $210.7 million and $305.4 million at June 30, 2026 and December 31, 2025, respectively, of advanced deposits of project costs and $10.0 million and zero, respectively, of regulatory assets at June 30, 2026 and December 31, 2025, respectively, of consolidated VIEs that may be used only to settle obligations of the consolidated VIEs. Refer to Note 4, "Noncontrolling Interests," for additional information.
[2] Includes $335.6 million and $56.9 million at June 30, 2026 and December 31, 2025, respectively, of current liabilities and $57.0 million and $55.7 million at June 30, 2026 and December 31, 2025, respectively, of other liabilities, and finance leases of $40.0 million and $40.1 million at June 30, 2026 and December 31, 2025, respectively, of consolidated VIEs that creditors do not have recourse to our general credit. Refer to Note 4, "Noncontrolling Interests," for additional information.
v3.26.1
Statements of Consolidated Balance Sheets (Parenthetical) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Amortized Cost $ 164.6 $ 145.8
Common Stock, Shares Authorized 750,000,000 750,000,000
Common Stock, Shares, Outstanding 479,498,053 478,432,058
Public Utilities, Property, Plant and Equipment, Net [1] $ 30,521.3 $ 28,688.2
Current assets [1] 2,199.4 2,377.2
Current liabilities [2] 4,414.5 3,457.4
Other Liabilities [2] 5,622.1 5,283.6
Joint Ventures    
Public Utilities, Property, Plant and Equipment, Net 1,764.0 1,312.7
Current assets 223.4 90.1
Current liabilities 335.6 56.9
Other Liabilities $ 57.0 $ 55.7
[1] Includes $1,764.0 million and $1,312.7 million at June 30, 2026 and December 31, 2025, respectively, of net property, plant and equipment assets and $223.4 million and $90.1 million at June 30, 2026 and December 31, 2025, respectively, of current assets of consolidated VIEs that may be used only to settle obligations of the consolidated VIEs. Refer to Note 4, "Noncontrolling Interests," for additional information.
(2)Includes $210.7 million and $305.4 million at June 30, 2026 and December 31, 2025, respectively, of advanced deposits of project costs and $10.0 million and zero, respectively, of regulatory assets at June 30, 2026 and December 31, 2025, respectively, of consolidated VIEs that may be used only to settle obligations of the consolidated VIEs. Refer to Note 4, "Noncontrolling Interests," for additional information.
[2] Includes $335.6 million and $56.9 million at June 30, 2026 and December 31, 2025, respectively, of current liabilities and $57.0 million and $55.7 million at June 30, 2026 and December 31, 2025, respectively, of other liabilities, and finance leases of $40.0 million and $40.1 million at June 30, 2026 and December 31, 2025, respectively, of consolidated VIEs that creditors do not have recourse to our general credit. Refer to Note 4, "Noncontrolling Interests," for additional information.
v3.26.1
Statements of Consolidated Cash Flows - USD ($)
$ in Millions
 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Operating Activities    
Net Income $ 593.1 $ 627.2
Adjustments to Reconcile Net Income to Net Cash from Operating Activities:    
Depreciation and amortization 650.5 545.3
Deferred income taxes and investment tax credits 107.6 120.4
Loss on sale of assets 0.0 0.8
Payments for asset retirement obligations (12.1) (31.3)
Other adjustments 38.2 22.3
Changes in Assets and Liabilities:    
Components of working capital(1) (272.0) (64.8)
Regulatory assets/liabilities (56.1) (23.7)
Deferred charges and other noncurrent assets 18.0 (14.9)
Other noncurrent liabilities and deferred credits and charges 55.5 0.5
Net Cash Flows from Operating Activities 1,122.7 1,181.8
Investing Activities    
Capital expenditures (1,902.6) (1,295.5)
Payment to renewable generation asset developer 0.0 (958.0)
Advanced deposits (92.1) (160.9)
Other investing activities (112.1) (151.9)
Net Cash Flows used for Investing Activities (2,106.8) (2,566.3)
Financing Activities    
Proceeds from issuance of long-term debt 1,239.7 2,362.0
Repayments of finance lease obligations (10.4) (10.9)
Net change in commercial paper and other short-term borrowings (44.0) (604.6)
Issuance of common stock, net of issuance costs 7.0 6.8
Equity costs, premiums and other debt related costs (24.7) (17.7)
Contributions from NIPSCO and GenCo minority interest holders 124.5 134.3
Distributions to tax equity partners (8.0) (9.8)
Distribution to NIPSCO minority interest holders (47.0) (44.4)
Dividends paid - common stock (293.3) (264.2)
Net Cash Flows from Financing Activities 943.8 1,551.5
Change in cash, cash equivalents and restricted cash (40.3) 167.0
Cash, cash equivalents and restricted cash at beginning of period 135.7 198.6
Cash, Cash Equivalents and Restricted Cash at End of Period $ 95.4 $ 365.6
v3.26.1
Statement of Consolidated Cash Flows (Schedule of Balance Sheet Reconciliation) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Jun. 30, 2025
Dec. 31, 2024
Cash and Cash Equivalent $ 70.0 $ 110.1    
Restricted Cash 25.4 25.6    
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents $ 95.4 $ 135.7 $ 365.6 $ 198.6
v3.26.1
Statements of Consolidated Cash Flows (Supplemental Disclosures of Cash Flow Information) - USD ($)
$ in Millions
 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]    
Capital expenditures included in current liabilities $ 678.8 $ 426.6
v3.26.1
Statements of Consolidated Equity - USD ($)
$ in Millions
Total
Common Stock
Treasury Stock, Common
Additional Paid-in Capital
Retained Deficit
Accumulated Other Comprehensive Income (Loss)
Noncontrolling Interest
Beginning balance at Dec. 31, 2024 $ 10,668.3 $ 4.7 $ (99.9) $ 9,521.5 $ (711.7) $ (30.4) $ 1,984.1
Comprehensive Income:              
Net Income 627.2       577.0    
Net current-period other comprehensive income (loss) 2.2            
Other comprehensive income (loss), net of tax 2.2 0.0 0.0 0.0 0.0 2.2 0.0
Dividends:              
Common stock (397.4)       (397.4)    
Contributions from noncontrolling interests (134.3)           (134.3)
Distributions to noncontrolling interests (54.2)   0.0       (54.2)
Stock Issuances:              
Employee stock purchase plan 3.6     3.6      
Long-term incentive plan       (8.1)      
401(k) and profit sharing 4.8     4.8      
Ending balance at Jun. 30, 2025 10,996.9 4.7 (99.9) 9,538.0 (532.1) (28.2) 2,114.4
Stock Issuances:              
Net income (loss) attributable to noncontrolling interest 50.2           50.2
Long-term incentive plan 8.1            
Beginning balance at Mar. 31, 2025 10,946.0 4.7 (99.9) 9,522.6 (501.4) (29.2) 2,049.2
Comprehensive Income:              
Net Income 100.5       102.2    
Net current-period other comprehensive income (loss) 1.0            
Other comprehensive income (loss), net of tax 1.0         1.0  
Dividends:              
Common stock (132.9)       (132.9)    
Contributions from noncontrolling interests (99.5)           (99.5)
Distributions to noncontrolling interests (32.6)           (32.6)
Stock Issuances:              
Employee stock purchase plan 1.9     1.9      
Long-term incentive plan 11.4            
401(k) and profit sharing 2.1     2.1      
Ending balance at Jun. 30, 2025 10,996.9 4.7 (99.9) 9,538.0 (532.1) (28.2) 2,114.4
Stock Issuances:              
Net income (loss) attributable to noncontrolling interest (1.7)           (1.7)
Long-term incentive plan       11.4      
Beginning balance at Dec. 31, 2025 11,659.9 4.8 (99.9) 9,866.6 (315.2) (6.2) 2,209.8
Comprehensive Income:              
Net Income 593.1       552.6    
Net current-period other comprehensive income (loss) (3.3)         (3.3)  
Other comprehensive income (loss), net of tax (3.3)            
Dividends:              
Common stock (437.2)       (437.2)    
Contributions from noncontrolling interests (124.5)           (124.5)
Distributions to noncontrolling interests (55.0)           (55.0)
Stock Issuances:              
Employee stock purchase plan 4.0     4.0      
401(k) and profit sharing 4.8     4.8      
Ending balance at Jun. 30, 2026 11,894.4 4.8 (99.9) 9,875.4 (196.2) (9.5) 2,319.8
Stock Issuances:              
Net income (loss) attributable to noncontrolling interest 40.5           40.5
Beginning balance at Mar. 31, 2026 11,927.5 4.8 (99.9) 9,859.1 (96.6) (9.2) 2,269.3
Comprehensive Income:              
Net Income 36.9       45.5    
Net current-period other comprehensive income (loss) (0.3)         (0.3)  
Other comprehensive income (loss), net of tax (0.3)            
Dividends:              
Common stock (145.1)       (145.1)    
Contributions from noncontrolling interests (91.0)           (91.0)
Distributions to noncontrolling interests (31.9)           (31.9)
Stock Issuances:              
Employee stock purchase plan 2.1     2.1      
Long-term incentive plan 12.0     12.0      
401(k) and profit sharing 2.2     2.2      
Ending balance at Jun. 30, 2026 11,894.4 $ 4.8 $ (99.9) $ 9,875.4 $ (196.2) $ (9.5) 2,319.8
Stock Issuances:              
Net income (loss) attributable to noncontrolling interest $ (8.6)           $ (8.6)
v3.26.1
Statements of Consolidated Equity (Shares) - shares
Total
Common Stock
Treasury Stock, Common
Issued:      
Shares, Issued (469,822,000)    
Beginning balance at Dec. 31, 2024   473,785,000  
Beginning balance at Dec. 31, 2024     3,963,000
Issued:      
Employee stock purchase plan 94,000 94,000 0
Long-term incentive plan 744,000 744,000 0
401(k) and profit sharing 124,000 124,000 0
Ending balance at Jun. 30, 2025 479,498,000    
Beginning balance at Dec. 31, 2024   473,785,000  
Beginning balance at Dec. 31, 2024     3,963,000
Ending balance at Jun. 30, 2025   483,461,000  
Ending balance at Jun. 30, 2025     3,963,000
Issued:      
Shares, Issued (470,618,000) (474,581,000)  
Beginning balance at Mar. 31, 2025     3,963,000
Issued:      
Employee stock purchase plan 48,000 48,000 0
Long-term incentive plan 62,000 62,000 0
401(k) and profit sharing 56,000 56,000 0
Ending balance at Jun. 30, 2025 479,498,000    
Beginning balance at Mar. 31, 2025     3,963,000
Ending balance at Jun. 30, 2025   483,461,000  
Ending balance at Jun. 30, 2025     3,963,000
Issued:      
Shares, Issued (470,784,000) (474,747,000)  
Beginning balance at Dec. 31, 2025 478,432,058    
Beginning balance at Dec. 31, 2025   482,395,000  
Beginning balance at Dec. 31, 2025     3,963,000
Issued:      
Employee stock purchase plan 90,000 90,000 0
Long-term incentive plan 873,000 873,000 0
401(k) and profit sharing 103,000 103,000 0
Ending balance at Jun. 30, 2026 479,498,053    
Beginning balance at Dec. 31, 2025   482,395,000  
Beginning balance at Dec. 31, 2025     3,963,000
Ending balance at Jun. 30, 2026   483,461,000  
Ending balance at Jun. 30, 2026     3,963,000
Beginning balance at Mar. 31, 2026 479,365,000    
Beginning balance at Mar. 31, 2026   483,328,000  
Beginning balance at Mar. 31, 2026     3,963,000
Issued:      
Employee stock purchase plan 45,000 45,000 0
Long-term incentive plan 42,000 42,000 0
401(k) and profit sharing 46,000 46,000 0
Ending balance at Jun. 30, 2026 479,498,053    
Beginning balance at Mar. 31, 2026   483,328,000  
Beginning balance at Mar. 31, 2026     3,963,000
Ending balance at Jun. 30, 2026   483,461,000  
Ending balance at Jun. 30, 2026     3,963,000
v3.26.1
Statements Of Consolidated Equity (Parenthetical) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Common Stock, Dividends, Per Share, Declared $ 0.30 $ 0.28 $ 0.90 $ 0.84
Preferred Stock, Redemption Amount     $ (3.6)  
Distributions to noncontrolling interests $ 91.0 $ 99.5 124.5 $ 134.3
Distributions to noncontrolling interests (31.9) (32.6) (55.0) (54.2)
Noncontrolling Interest        
Preferred Stock, Redemption Amount     0.0  
Distributions to noncontrolling interests 91.0 99.5 124.5 134.3
Distributions to noncontrolling interests $ (31.9) $ (32.6) (55.0) (54.2)
Common Stock        
Preferred Stock, Redemption Amount     0.0  
Treasury Stock, Common        
Preferred Stock, Redemption Amount     0.0  
Distributions to noncontrolling interests       $ 0.0
Additional Paid-in Capital        
Preferred Stock, Redemption Amount     0.0  
Retained Deficit        
Preferred Stock, Redemption Amount     3.6  
Accumulated Other Comprehensive Income (Loss)        
Preferred Stock, Redemption Amount     $ 0.0  
v3.26.1
Statements of Consolidated Balance Sheets - USD ($)
$ in Millions
 6 Months Ended 12 Months Ended
Jun. 30, 2026
Dec. 31, 2025
Statement of Financial Position [Abstract]    
Increase (Decrease) in Other Regulatory Assets $ 10.0 $ 0.0
v3.26.1
Basis of Accounting Presentation
 6 Months Ended
Jun. 30, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Basis of Accounting Presentation
Our accompanying Condensed Consolidated Financial Statements (unaudited) reflect all normal recurring adjustments that are necessary, in the opinion of management, to present fairly the results of operations in accordance with GAAP in the United States of America. The accompanying financial statements include the accounts of us, our majority-owned subsidiaries, and VIEs of which we are the primary beneficiary after the elimination of all intercompany accounts and transactions.
The accompanying financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the fiscal year ended December 31, 2025. Income for interim periods may not be indicative of results for the calendar year due to weather variations and other factors.
The Condensed Consolidated Financial Statements (unaudited) have been prepared pursuant to the rules and regulations of the SEC. Certain information and note disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to those rules and regulations, although we believe that the disclosures made in this Quarterly Report on Form 10-Q are adequate to make the information herein not misleading.
v3.26.1
Revenue Recognition
 6 Months Ended
Jun. 30, 2026
Revenue from Contract with Customer [Abstract]  
Revenue from Contract with Customer
Revenue Disaggregation and Reconciliation. We disaggregate revenue from contracts with customers based upon reportable segment, as well as by customer class. The Columbia Operations segment provides regulated natural gas service and transportation for residential, commercial and industrial customers in Ohio, Pennsylvania, Virginia, Kentucky, and Maryland. The NIPSCO Operations segment provides regulated gas and electric service in the northern part of Indiana.
The tables below reconcile revenue disaggregation by customer class to segment revenue, as well as to revenues reflected on the Condensed Statements of Consolidated Income (unaudited):
Three months ended June 30, 2026
(in millions)
Columbia OperationsNIPSCO OperationsCorporate and OtherTotal
Gas Distribution
Residential$399.9 $102.2 $— $502.1 
Commercial124.6 41.4 — 166.0 
Industrial40.3 21.0 — 61.3 
Off-system11.5 — — 11.5 
Miscellaneous(1)
8.5 3.0 — 11.5 
Subtotal$584.8 $167.6 $— $752.4 
Electric Generation and Power Delivery
Residential— 183.1 — 183.1 
Commercial— 181.7 — 181.7 
Industrial— 159.2 — 159.2 
Wholesale— 9.9 — 9.9 
Public Authority— 3.7 — 3.7 
Miscellaneous(1)
— (0.5)— (0.5)
Subtotal $— $537.1 $— $537.1 
Total Customer Revenues(2)
584.8 704.7 — 1,289.5 
Other Revenues(3)
12.2 39.2 1.5 52.9 
Total Operating Revenues$597.0 $743.9 $1.5 $1,342.4 
(1)Amounts included in Columbia Operations primarily relate to earnings share mechanisms, late fees, and wholesale revenues. Amounts included in NIPSCO Operations primarily relate to late fees, property rentals, transmission revenue, and offsetting regulatory program deferrals. (2)Customer revenue amounts exclude intersegment revenues. See Note 17, "Business Segment Information," for discussion of intersegment revenues.
(3)Amounts included in Columbia Operations primarily relate to alternative revenue programs including weather normalization adjustment mechanisms. Amounts included in NIPSCO Operations primarily relate to alternative revenue programs including weather normalization adjustment mechanisms, MISO multi-value projects and revenue from FERC jurisdictional transmission assets. Amounts included in Corporate and Other primarily relate to products and services revenue.
Three months ended June 30, 2025
(in millions)
Columbia Operations
NIPSCO Operations
Corporate and OtherTotal
Gas Distribution
Residential$397.0 $114.2 $— $511.2 
Commercial126.2 45.5 — 171.7 
Industrial37.6 22.6 — 60.2 
Off-system22.8 — — 22.8 
Miscellaneous(1)
8.7 3.3 — 12.0 
Subtotal$592.3 $185.6 $— $777.9 
Electric Generation and Power Delivery
Residential$— $163.9 $— $163.9 
Commercial— 161.0 — 161.0 
Industrial— 133.5 — 133.5 
Wholesale— 11.9 — 11.9 
Miscellaneous(1)
— (1.7)— (1.7)
Subtotal$— $468.6 $— $468.6 
Total Customer Revenues(2)
592.3 654.2 — 1,246.5 
Other Revenues(3)
8.9 26.4 1.2 36.5 
Total Operating Revenues$601.2 $680.6 $1.2 $1,283.0 
(1)Amounts included in Columbia Operations primarily relate to earnings share mechanisms and late fees. Amounts included in NIPSCO Operations primarily relate to late fees and property rentals. (2)Customer revenue amounts exclude intersegment revenues. See Note 17, "Business Segment Information," for discussion of intersegment revenues.
(3)Amounts included in Columbia Operations primarily relate to alternative revenue programs including weather normalization adjustment mechanisms. Amounts included in NIPSCO Operations primarily relate to alternative revenue programs including weather normalization adjustment mechanisms, MISO multi-value projects and revenue from FERC jurisdictional transmission assets. Amounts included in Corporate and Other primarily relate to products and services revenue.
Six months ended June 30, 2026
(in millions)
Columbia OperationsNIPSCO OperationsCorporate and OtherTotal
Gas Distribution
Residential$1,309.1 $420.8 $— $1,729.9 
Commercial455.6 157.0 — 612.6 
Industrial97.7 55.1 — 152.8 
Off-system28.3 — — 28.3 
Miscellaneous(1)
22.7 6.1 — 28.8 
Subtotal$1,913.4 $639.0 $— $2,552.4 
Electric Generation and Power Delivery
Residential$— $359.9 $— $359.9 
Commercial— 353.8 — 353.8 
Industrial— 314.7 — 314.7 
Wholesale— 18.4 — 18.4 
Public Authority— 8.0 — 8.0 
Miscellaneous(1)
— 4.6 — 4.6 
Subtotal$— $1,059.4 $— $1,059.4 
Total Customer Revenues(2)
1,913.4 1,698.4 — 3,611.8 
Other Revenues(3)
6.8 84.0 2.9 93.7 
Total Operating Revenues$1,920.2 $1,782.4 $2.9 $3,705.5 
(1)Amounts included in Columbia Operations are primarily relate to earnings share mechanisms, late fees, and wholesale revenues. Amounts included in NIPSCO Operations primarily relate to late fees, property rentals, transmission revenue, and offsetting regulatory program deferrals. (2)Customer revenue amounts exclude intersegment revenues. See Note 17, "Business Segment Information," for discussion of intersegment revenues.
(3)Amounts included in Columbia Operations primarily relate to alternative revenue programs including weather normalization adjustment mechanisms. Amounts included in NIPSCO Operations primarily relate to alternative revenue programs including weather adjustment mechanisms, MISO multi-value projects and revenue from FERC jurisdictional transmission assets. Amounts included in Corporate and Other primarily relate to products and services revenue.
Six months ended June 30, 2025
(in millions)
Columbia OperationsNIPSCO OperationsCorporate and OtherTotal
Gas Distribution
Residential$1,248.2 $405.6 $— $1,653.8 
Commercial432.7 148.6 — 581.3 
Industrial85.5 54.0 — 139.5 
Off-system45.1 — — 45.1 
Miscellaneous(1)
20.7 8.0 — 28.7 
Subtotal$1,832.2 $616.2 $— $2,448.4 
Electric Generation and Power Delivery
Residential$— $331.8 $— $331.8 
Commercial— 321.1 — 321.1 
Industrial— 276.1 — 276.1 
Wholesale— 19.5 — 19.5 
Miscellaneous(1)
— (0.9)— (0.9)
Subtotal$— $947.6 $— $947.6 
Total Customer Revenues(2)
1,832.2 1,563.8 — 3,396.0 
Other Revenues(3)
9.6 58.2 2.4 70.2 
Total Operating Revenues$1,841.8 $1,622.0 $2.4 $3,466.2 
(1)Amounts included in Columbia Operations are primarily relate to earnings share mechanisms and late fees. Amounts included in NIPSCO Operations, primarily relate to revenue refunds, public repairs and property rentals. (2)Customer revenue amounts exclude intersegment revenues. See Note 17, "Business Segment Information," for discussion of intersegment revenues.
(3)Amounts included in Columbia Operations primarily relate to weather normalization adjustment mechanisms. Amounts included in NIPSCO Operations primarily relate to MISO multi-value projects and revenue from FERC jurisdictional transmission assets. Amounts included in Corporate and Other primarily relate to products and services revenue.
Customer Accounts Receivable. Accounts receivable on our Condensed Consolidated Balance Sheets (unaudited) includes both billed and unbilled amounts, as well as certain amounts that are not related to customer revenues. Unbilled amounts of accounts receivable relate to a portion of a customer’s consumption of gas or electricity from the date of the last cycle billing through the last day of the month (balance sheet date). Factors taken into consideration when estimating unbilled revenue include historical usage, customer rates, and weather. A significant portion of our operations are subject to seasonal fluctuations in sales. During the heating season, primarily from November through March, revenues and receivables from gas sales are more significant than in other months. The balances of customer receivables as of June 30, 2026 and December 31, 2025 are presented in the table below. Contract liability balances were $95.0 million and zero as of June 30, 2026 and December 31, 2025, respectively. The increase was primarily attributable to consideration received in advance under a customer arrangement. Additionally, we have not incurred any significant costs to obtain or fulfill contracts.
(in millions)Customer Accounts Receivable, Billed (less reserve)Customer Accounts Receivable, Unbilled (less reserve)
Balance as of December 31, 2025$698.8 $465.2 
Balance as of June 30, 2026$694.5 $118.0 
Utility revenues are billed to customers monthly on a cycle basis. We expect that substantially all customer accounts receivable will be collected following customer billing, as this revenue consists primarily of periodic, tariff-based billings for service and usage. We maintain common utility credit risk mitigation practices, including requiring deposits and actively pursuing collection of past due amounts. Our regulated operations also utilize certain regulatory mechanisms that facilitate recovery of bad debt costs within tariff-based rates, which provides further evidence of collectability. It is probable that substantially all of the consideration to which we are entitled from customers will be collected upon satisfaction of performance obligations.
Allowance for Credit Losses. To evaluate for expected credit losses, customer account receivables are pooled based on similar risk characteristics, such as customer type, geography, payment terms, and related macro-economic risks. Expected credit losses are established using a model that considers historical collections experience, current information, and reasonable and supportable forecasts. Internal and external inputs are used in our credit model including, but not limited to, revenue projections, actual charge-offs data, recoveries data, shut-offs, security deposits and final bill data. We continuously evaluate available information relevant to assessing collectability of current and future receivables. We evaluate creditworthiness of specific customers periodically or following changes in facts and circumstances. When we become aware of a specific commercial or industrial customer's inability to pay, an allowance for expected credit losses is recorded for the relevant amount. We also monitor other circumstances that could affect our overall expected credit losses including, but not limited to, creditworthiness of overall population in service territories, adverse conditions impacting an industry sector, and current economic conditions.
At each reporting period, we record expected credit losses to an allowance for credit losses account. When deemed to be uncollectible, customer accounts are written-off. Rollforwards of our allowance for credit losses as of June 30, 2026 and December 31, 2025 are presented in the table below:

(in millions)
Columbia Operations
NIPSCO Operations
Total
Balance as of December 31, 2025$15.6 $25.0 $40.6 
Current period provisions24.4 10.2 34.6 
Write-offs charged against allowance(30.2)(10.2)(40.4)
Recoveries of amounts previously written off4.7 0.7 5.4 
Balance as of June 30, 2026$14.5 $25.7 $40.2 
(in millions)
Columbia Operations
NIPSCO Operations
Total
Balance as of December 31, 2024$9.8 $13.9 $23.7 
Current period provisions42.3 25.0 67.3 
Write-offs charged against allowance(50.8)(15.0)(65.8)
Recoveries of amounts previously written off14.3 1.1 15.4 
Balance as of December 31, 2025$15.6 $25.0 $40.6 
v3.26.1
Earnings Per Share
 6 Months Ended
Jun. 30, 2026
Earnings Per Share [Abstract]  
Earnings Per Share
The calculations of basic and diluted EPS are based on the weighted average number of shares of common stock and potential common stock outstanding during the period. Diluted EPS includes the incremental effects of the various long-term incentive compensation plans and ATM forward sale agreements under the treasury stock method when the impact would be dilutive (See Note 6, "Equity").

We use the two-class method of computing earnings per share because we have participating securities in the form of non-vested restricted stock units with a non-forfeitable right to dividend equivalents, for which vesting is predicated solely on the passage of time. The calculation of earnings per share using the two-class method excludes income attributable to these participating securities from the numerator and excludes the dilutive impact of those shares from the denominator.

The following table presents the calculation of our basic and diluted EPS:
Three Months Ended
June 30,		Six Months Ended
June 30,
(in millions, except per share amounts)2026202520262025
Numerator:
Net Income Available to Common Shareholders
$45.5 $102.2 $556.2 $577.0 
Less: Income allocated to participating securities0.1 0.3 1.2 1.1 
Net Income Available to Common Shareholders - Basic
45.4 101.9 555.0 575.9 
Net Income Available to Common Shareholders - Diluted
$45.4 $101.9 $555.0 $575.9 
Denominator:
Average common shares outstanding - Basic479.7 471.0 479.4 470.6 
Dilutive potential common shares:
Shares contingently issuable under employee stock plans1.1 1.0 1.3 1.2 
Shares restricted under employee stock plans0.1 0.1 0.1 0.5 
ATM forward sale agreements
0.3 — 0.2 
Average Common Shares - Diluted481.2 472.1 481.0 472.3 
Earnings per common share:
Basic$0.10 $0.22 $1.16 $1.22 
Diluted$0.09 $0.22 $1.15 $1.22 
v3.26.1
Equity
 6 Months Ended
Jun. 30, 2026
Equity [Abstract]  
Equity Equity
ATM Program. In October 2025, we entered into eleven separate equity distribution agreements providing for the sale up to an aggregate of $1.5 billion of our common stock.

•In October 2025, we executed a forward sale agreement, which allows us to issue a fixed number of shares at a price to be settled in the future. The forward purchaser under our forward sale agreement borrowed 2,390,057 shares from third parties, which the forward purchaser sold, through its affiliated agent, at a weighted average price of $41.84 per share. We may settle the forward sale agreement in shares, cash or net shares by October 2026. Had we settled all of the shares under the forward sale agreement at June 30, 2026, we would have received approximately $99.7 million, based on a net price of $41.72 per share.

•In February 2026, we executed a forward sale agreement, which allows us to issue a fixed number of shares at a price to be settled in the future. The forward purchaser under our forward sale agreement borrowed 2,200,000 shares from third parties, which the forward purchaser sold, through its affiliated agent, at a weighted average price of $45.63 per share. We may settle the forward sale agreement in shares, cash or net shares by December 2026. Had we settled all of the shares under the forward sale agreement at June 30, 2026, we would have received approximately $100.0 million, based on a net price of $45.46 per share.

•In June 2026, we executed a forward sale agreement, which allows us to issue a fixed number of shares at a price to be settled in the future. The forward purchaser under our forward sale agreement borrowed 2,151,874 shares from third parties, which the forward purchaser sold, through its affiliated agent, at a weighted average price of $46.47 per share. We may settle the forward sale agreement in shares, cash or net shares by December 2026. Had we settled all of the shares under the forward sale agreement at June 30, 2026, we would have received approximately $99.2 million, based on a net price of $46.10 per share.

•As of June 30, 2026, the ATM program inclusive of the outstanding forward sale agreements had approximately $1.15 billion of equity capacity available. The ATM program expires in December 2028.

Preferred Stock. During the first quarter of 2026, following the issuance of final U.S. Treasury and Internal Revenue Service regulations clarifying the scope and application of the federal excise tax on stock repurchases made after December 31, 2022, we evaluated the applicability of the excise tax to our 2023 Series A Preferred Stock redemption premium. Based on this assessment, we determined that the excise tax previously recorded does not apply to these share repurchases. Accordingly, we reversed approximately $3.6 million of excise tax expense and recognized a receivable as of June 30, 2026, for the expected refund of the amounts previously remitted.
v3.26.1
Regulatory Matters
 6 Months Ended
Jun. 30, 2026
Regulatory Assets and Liabilities Disclosure [Abstract]  
Regulatory Matters
Regulatory Assets and Liabilities. We follow the accounting and reporting requirements of ASC Topic 980, which provides that regulated entities account for and report assets and liabilities consistent with the economic effect of regulatory rate-making procedures when the rates established are designed to recover the costs of providing the regulated service and it is probable that such rates will be charged to and collected from customers. Certain expenses and credits subject to utility regulation or rate determination normally reflected in income or expense are deferred on the balance sheet and are recognized in the income statement as the related amounts are included in customer rates and recovered from or refunded to customers. We assess the probability of collection for all of our regulatory assets each period. The offset to the regulatory liability associated with our renewable investments included in regulated rates is recorded in "Depreciation and amortization" on the Condensed Statements of Consolidated Income (unaudited).
v3.26.1
Risk Management Activities
 6 Months Ended
Jun. 30, 2026
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Risk Management Activities Risk Management Activities
We are exposed to certain risks relating to our ongoing business operations, namely commodity price risk and interest rate risk. We recognize that the prudent and selective use of derivatives may help to limit volatility in the price of natural gas and manage interest rate exposure.
Risk management assets and liabilities on our derivatives are presented on the Condensed Consolidated Balance Sheets (unaudited) as shown below:
June 30, 2026December 31, 2025
(in millions)Assets LiabilitiesAssetsLiabilities
Current(1)
Derivatives not designated as hedging instruments$2.9 $3.5 $9.7 $2.1 
Total$2.9 $3.5 $9.7 $2.1 
Noncurrent(2)
Derivatives not designated as hedging instruments$8.7 $10.8 $9.1 $3.8 
Total$8.7 $10.8 $9.1 $3.8 
(1)Current assets and liabilities are presented in "Other current assets" and "Other accruals", respectively, on the Condensed Consolidated Balance Sheets (unaudited).
(2)Noncurrent assets and liabilities are presented in "Deferred charges and other" and "Other noncurrent liabilities", respectively, on the Condensed Consolidated Balance Sheets (unaudited).
Our derivative instruments are subject to enforceable master netting arrangements or similar agreements. No collateral was either received or posted related to our outstanding derivative positions at June 30, 2026. If the above gross asset and liability positions were presented net of amounts owed or receivable from counterparties, we would report a net liability position of $2.7 million and a net asset position of $12.9 million as of June 30, 2026 and December 31, 2025, respectively.
Derivatives Not Designated as Hedging Instruments
Commodity price risk management. We, along with our utility customers, are exposed to variability in cash flows associated with natural gas purchases and volatility in natural gas prices. We purchase natural gas for sale and delivery to our retail, commercial and industrial customers, and for most customers the variability in the market price of gas is passed through in their rates. Some of our utility subsidiaries offer programs whereby variability in the market price of gas is assumed by the respective utility. The objective of our commodity price risk programs is to mitigate the gas cost variability, for our customers, associated with natural gas purchases or sales by economically hedging the various gas cost components using a combination of futures, options, forwards or other derivative contracts. As of June 30, 2026 and December 31, 2025, we had 80.9 MMDth and 83.7 MMDth, respectively, of net energy derivative volumes outstanding related to our natural gas hedges.
NIPSCO has received IURC approval to lock in a fixed price for its natural gas customers using long-term forward purchase instruments and is limited to 20% of NIPSCO's average annual GCA purchase volume. As of June 30, 2026, the remaining terms of these instruments range from one to six years. Likewise, Columbia of Pennsylvania has received approval for a 24-month rolling hedge program that will continue in perpetuity. The program is designed to financially hedge approximately 20% of the customers' annual demand. Under both programs, all gains and losses on these derivative contracts are deferred as regulatory liabilities or assets and are remitted to or collected from customers through the relevant cost recovery mechanism.
The following table summarizes the gains and losses associated with the commodity price risk programs deferred as regulatory assets and liabilities:
(in millions)June 30, 2026December 31, 2025
Regulatory Assets
Losses on commodity price risk programs$20.3 $10.1 
Regulatory Liabilities
Gains on commodity price risk programs$12.2 $19.2 
Our derivative instruments measured at fair value as of June 30, 2026 and December 31, 2025 do not contain any credit-risk-related contingent features.
Derivatives Designated as Hedging Instruments

Interest rate risk management. As of June 30, 2026 and December 31, 2025, we had no active interest rate swap positions. We
have recorded the overall net loss related to previously settled interest rate swaps in AOCI. The gain or loss associated with each previously settled interest rate swap is amortized in interest expense over the term of each corresponding debt issuance. These amounts were immaterial for the three and six months ended June 30, 2026 and 2025 and are recorded in "Interest expense, net" on the Condensed Statements of Consolidated Income (unaudited). Amounts expected to be reclassified to earnings during the next twelve months are immaterial. See Note 16, "Accumulated Other Comprehensive Loss," for additional information.
v3.26.1
Fair Value
 6 Months Ended
Jun. 30, 2026
Fair Value Disclosures [Abstract]  
Fair Value
A.    Fair Value Measurements
Recurring Fair Value Measurements
The following tables present financial assets and liabilities measured and recorded at fair value on our Condensed Consolidated Balance Sheets (unaudited) on a recurring basis and their level within the fair value hierarchy as of June 30, 2026 and December 31, 2025. As of June 30, 2026 and December 31, 2025, there were no material transfers between fair value hierarchies. Additionally, there were no changes in the method or significant assumptions used to estimate the fair value of our financial instruments.
Recurring Fair Value Measurements
June 30, 2026 (in millions)
Quoted Prices in
Active Markets
for Identical
Assets
(Level 1)		Significant
Other
Observable
Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)
Balance as of
June 30, 2026
Assets
Risk management assets$— $11.6 $— $11.6 
Available-for-sale debt securities— 163.3 — 163.3 
Equity securities(1)(2)
9.4 — — 9.4 
Total$9.4 $174.9 $— $184.3 
Liabilities
Risk management liabilities$— $14.3 $— $14.3 
Total$— $14.3 $— $14.3 
(1)Equity securities are in a high dividend equity fund and are valued using market prices in active markets. Level 1 instrument valuations are obtained from real-time quotes for transactions in active exchange markets involving identical assets. Equity securities are presented in "Other Investments" on the Condensed Consolidated Balance Sheets (unaudited).
(2)As of June 30, 2026, the investment cost of equity securities measured at fair value was $7.9 million, gross unrealized gains were $1.6 million, and the fair value was $9.4 million.
Recurring Fair Value Measurements
December 31, 2025 (in millions)
Quoted Prices in
Active Markets
for Identical
Assets
(Level 1)		Significant
Other
Observable
Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)
Balance as of
December 31, 2025
Assets
Risk management assets$— $18.8 $— $18.8 
Available-for-sale debt securities— 146.1 — 146.1 
Equity Securities(1)(2)
8.5 — — 8.5 
Total$8.5 $164.9 $— $173.4 
Liabilities
Risk management liabilities$— $5.9 $— $5.9 
Total$— $5.9 $— $5.9 
(1)Equity securities are in a high dividend equity fund and are valued using market prices in active markets. Level 1 instrument valuations are obtained from real-time quotes for transactions in active exchange markets involving identical assets. Equity securities are presented in "Other Investments" on the Condensed Consolidated Balance Sheets (unaudited).
(2)As of December 31, 2025, the investment cost of equity securities measured at fair value was $7.9 million, gross unrealized gains were $0.7 million, and the fair value was $8.5 million.

Level 1- When utilized, exchange-traded derivative contracts are based on unadjusted quoted prices in active markets and are classified within Level 1. These financial assets and liabilities are secured with cash on deposit with the exchange; therefore, nonperformance risk has not been incorporated into these valuations. These financial assets and liabilities are deemed to be cleared and settled daily by NYMEX as the related cash collateral is posted with the exchange. As a result of this exchange rule, NYMEX derivatives are considered to have no fair value at the balance sheet date for financial reporting purposes, and are presented in Level 1 net of posted cash; however, the derivatives remain outstanding and are subject to future commodity price fluctuations until they are settled in accordance with their contractual terms.
Level 2- Certain non-exchange-traded derivatives are valued using broker or over-the-counter, on-line exchanges. In such cases, these non-exchange-traded derivatives are classified within Level 2. Non-exchange-based derivative instruments include swaps, forwards, and options. In certain instances, these instruments may utilize models to measure fair value taking into consideration credit risk. We use a similar model to value similar instruments. Valuation models utilize various inputs that include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, other observable inputs for the asset or liability and market-corroborated inputs, (i.e., inputs derived principally from or corroborated by observable market data by correlation or other means). Where observable inputs are available for substantially the full term of the asset or liability, the instrument is categorized within Level 2.
Level 3- Certain derivatives trade in less active markets with a lower availability of pricing information and models may be utilized in the valuation. When such inputs have a significant impact on the measurement of fair value, the instrument is categorized within Level 3.
Risk Management Assets and Liabilities. Risk management assets and liabilities include exchange-traded NYMEX futures and NYMEX options and non-exchange-based forward purchase contracts. NIPSCO and Columbia of Pennsylvania have entered into long-term forward natural gas purchase instruments to lock in a fixed price for natural gas customers. We value these contracts using a pricing model that incorporates market-based information when available, as these instruments trade less frequently and are classified within Level 2 of the fair value hierarchy. For additional information, see Note 10, "Risk Management Activities."
Available-for-Sale Debt Securities. Available-for-sale debt securities are investments pledged as collateral for trust accounts related to our wholly owned insurance company. We value U.S. Treasury, corporate debt and mortgage-backed securities using a matrix pricing model that incorporates market-based information. These securities trade less frequently and are classified within Level 2 of the fair value hierarchy.
Our available-for-sale debt securities impairments are recognized periodically using an allowance approach. At each reporting date, we utilize a quantitative and qualitative review process to assess the impairment of available-for-sale debt securities at the individual security level. For securities in a loss position, we evaluate our intent to sell or whether it is more-likely-than-not that we will be required to sell the security prior to the recovery of its amortized cost. If either criteria is met, the loss is recognized in earnings immediately, with the offsetting entry to the carrying value of the security. If both criteria are not met, we perform
an analysis to determine whether the unrealized loss is related to credit factors. The analysis focuses on a variety of factors that include, but are not limited to, downgrade on ratings of the security, defaults in the current reporting period or projected defaults in the future, the security's yield spread over treasuries, and other relevant market data. If the unrealized loss is not related to credit factors, it is included in other comprehensive income. If the unrealized loss is related to credit factors, the loss is recognized as credit loss expense in earnings during the period, with an offsetting entry to the allowance for credit losses. The amount of the credit loss recorded to the allowance account is limited by the amount at which the security's fair value is less than its amortized cost basis. If certain amounts recorded in the allowance for credit losses are deemed uncollectible, the allowance on the uncollectible portion will be charged off, with an offsetting entry to the carrying value of the security. Subsequent improvements to the estimated credit losses of available-for-sale debt securities will be recognized immediately in earnings. Continuous credit monitoring and portfolio credit balancing mitigates our risk of credit losses on our available-for-sale debt securities.

The amortized cost, gross unrealized gains and losses, allowance for credit losses, and fair value of available-for-sale securities at June 30, 2026 and December 31, 2025 were: 
June 30, 2026 (in millions)
Amortized
Cost		Gross Unrealized Gains
Gross Unrealized Losses(1)
Fair
Value
Available-for-sale debt securities
U.S. Treasury debt securities$10.4 $— $(0.1)$10.3 
Corporate/Other debt securities154.2 1.4 (2.6)153.0 
Total$164.6 $1.4 $(2.7)$163.3 
December 31, 2025 (in millions)
Amortized
Cost		Gross Unrealized Gains
Gross Unrealized Losses(2)
Fair
Value
Available-for-sale debt securities
U.S. Treasury debt securities$9.5 $— $— $9.5 
Corporate/Other debt securities136.3 2.4 (2.1)136.6 
Total$145.8 $2.4 $(2.1)$146.1 
(1)Fair value of U.S. Treasury debt securities and Corporate/Other debt securities in an unrealized loss position without an allowance for credit losses is $8.7 million and $74.2 million, respectively, at June 30, 2026.
(2)Fair value of U.S. Treasury debt securities and Corporate/Other debt securities in an unrealized loss position without an allowance for credit losses is $3.5 million and $40.2 million, respectively, at December 31, 2025.
The cost of maturities sold is based upon specific identification. Net realized gains and losses on available-for-sale securities were $0.1 million for the three and six months ended June 30, 2026 and 2025, respectively. At June 30, 2026, approximately $10.6 million and $5.8 million of Corporate/Other debt securities and U.S. Treasury debt securities, respectively, had maturities of less than a year.
Equity Investments. Investments measured at net asset value per share (or its equivalent) as a practical expedient have not been classified in the fair value hierarchy. These investments represent holdings in a single private investment fund that are redeemable at the election of the holder. As of June 30, 2026 and December 31, 2025, the Company holds $18.4 million and $17.9 million of equity investments measured at net asset value, respectively.
Non-recurring Fair Value Measurements
We measure the fair value of certain assets, including goodwill, on a non-recurring basis, typically when events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. As of June 30, 2026, no non-recurring fair value adjustments have been made.
B.    Other Fair Value Disclosures for Financial Instruments. The carrying amount of cash and cash equivalents, restricted cash, notes receivable, customer deposits and short-term borrowings is a reasonable estimate of fair value due to their liquid or short-term nature. Our long-term borrowings are recorded at historical amounts.
The following method and assumptions were used to estimate the fair value of each class of financial instruments.
Long-term Debt. The fair value of outstanding long-term debt is estimated based on the quoted market prices for the same or similar securities. Certain premium costs associated with the early settlement of long-term debt are not taken into consideration in determining fair value. These fair value measurements are classified within Level 2 of the fair value hierarchy. As of June 30, 2026, there was no change in the method or significant assumptions used to estimate the fair value of long-term debt.
The carrying amount and estimated fair values of these financial instruments were as follows: 
(in millions)
Carrying
Amount as of
June 30, 2026
Estimated Fair
Value as of
June 30, 2026
Carrying
Amount as of
Dec. 31, 2025
Estimated Fair
Value as of
Dec. 31, 2025
Long-term debt (including current portion)$16,711.0 $16,015.4 $15,477.5 $14,975.3 
v3.26.1
Income Taxes
 6 Months Ended
Jun. 30, 2026
Income Tax Disclosure [Abstract]  
Income Taxes
Our interim effective tax rates reflect the estimated annual effective tax rates for 2026 and 2025 applied to year-to-date pretax income, adjusted for tax expense associated with certain discrete items. The effective tax rates for the three months ended June 30, 2026 and 2025 were 21.7% and 19.1%, respectively. The effective tax rates for the six months ended June 30, 2026 and 2025 were 13.9% and 17.1%, respectively. These effective tax rates differ from the federal statutory tax rate of 21% primarily due to net income attributable to noncontrolling interest, amortization of excess deferred income taxes, federal investment and production tax credits net of deferred regulatory liabilities, state income taxes, and other permanent book-to-tax differences.

The increase in the three month effective tax rate of 2.6% in 2026 compared to 2025 is primarily driven by lower federal investment and production tax credits net of pass back and decreased amortization of excess deferred income taxes, partially offset by a decrease in state tax expense and higher AFUDC equity.

The decrease in the six month effective tax rate of 3.2% in 2026 compared to 2025 is primarily driven by higher federal investment and production credit pass back realized during 2026.

As of June 30, 2026, there have been no material changes to our unrecognized tax benefits or possible changes that could reasonably be expected to occur during the next twelve months. See Note 15 to the Company’s Consolidated Financial Statements in the Annual Report on Form 10-K for the year ended December 31, 2025, for a discussion of these unrecognized tax benefits.
v3.26.1
Pension And Other Postretirement Benefits
 6 Months Ended
Jun. 30, 2026
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]  
Pension And Other Postretirement Benefits
We provide defined contribution plans and noncontributory defined benefit retirement plans that cover certain of our employees. Benefits under the defined benefit retirement plans reflect the employees' compensation, years of service and age at retirement. Additionally, we provide health care and life insurance benefits for certain retired employees. Certain active employees may become eligible for these benefits if they reach retirement age while working for us. The expected cost of such benefits is accrued during the employees' years of service. We determined that, for certain rate-regulated subsidiaries, the future
recovery of postretirement benefit costs is probable, and we record regulatory assets and liabilities for amounts that would otherwise have been recorded to expense or accumulated other comprehensive loss. Current rates of rate-regulated companies include postretirement benefit costs, including amortization of the regulatory assets and liabilities that arose prior to inclusion of these costs in rates. For most plans, cash contributions are remitted to grantor trusts.
For the six months ended June 30, 2026 and 2025, we contributed $2.6 million and $1.0 million, respectively, to our pension plans and $11.1 million and $10.5 million, respectively, to our OPEB plans.
The following table provides the components of the plans' actuarially determined net periodic benefit cost for the three and six months ended June 30, 2026 and 2025:
Pension BenefitsOPEB
Three Months Ended June 30, (in millions)
2026202520262025
Components of Net Periodic Benefit Cost(1)
Service cost$5.2 $4.9 $0.9 $1.0 
Interest cost14.1 16.0 4.6 5.6 
Expected return on assets(22.5)(23.1)(4.2)(4.2)
Amortization of prior service credit— — (1.1)(0.4)
Recognized actuarial loss5.9 6.4 — 0.4 
Total Net Periodic Benefit Cost $2.7 $4.2 $0.2 $2.4 
(1)The service cost component and all non-service cost components of net periodic benefit (income) cost are presented in "Operation and maintenance" and "Other, net," respectively, on the Condensed Statements of Consolidated Income (unaudited).
v3.26.1
Variable Interest Entities
 6 Months Ended
Jun. 30, 2026
Variable Interest Entities [Abstract]  
Variable Interest Entities . A VIE is an entity in which the controlling interest is determined through means other than a majority voting interest. NIPSCO is the managing member and operator of two wind JVs, Rosewater and Indiana Crossroads Wind, which have 102 MW and 302 MW of nameplate capacity, respectively. NIPSCO is also a managing member and operator of two solar JVs, Indiana Crossroads Solar and Dunn's Bridge I, which have a nameplate capacity of 200 MW and 265 MW, respectively. We have determined that these JVs are VIEs. NIPSCO controls decisions that are significant to these entities' ongoing operations and economic results. Therefore, we have concluded that NIPSCO is the primary beneficiary and have consolidated all four entities.
Members of each respective JV include NIPSCO (who is the managing member) and a tax equity partner. Earnings, tax attributes and cash flows are allocated to both NIPSCO and the tax equity partner in varying percentages by category and over the life of the partnership. NIPSCO and each tax equity partner contributed cash to the respective JV. Once the tax equity partner has earned their negotiated rate of return and after a stated contractual date, NIPSCO has the option to purchase the remaining interest in the respective JV, at fair market value, from the tax equity partner. NIPSCO has an obligation to purchase 100% of the electricity generated by each JV.
We did not provide any financial or other support for the JVs during the quarter that was not contractually required.
Our Condensed Consolidated Balance Sheets (unaudited) included the following assets and liabilities associated with the JV VIEs.
(in millions)June 30, 2026December 31, 2025
Net property, plant and equipment
$1,233.9 $1,273.0 
Current assets49.1 27.6 
Total assets(1)
1,283.0 1,300.6 
Current liabilities13.1 16.1 
Asset retirement obligations57.0 55.7 
Finance lease obligations
40.0 40.1 
Total liabilities(1)(2)
$110.1 $111.9 
(1)The assets of each VIE represent assets of a consolidated VIE that can be used only to settle obligations of the respective consolidated VIE. The creditors of the liabilities of the VIEs do not have recourse to the general credit of the primary beneficiary.
(2)In addition to the amounts disclosed above there is a de minimis amount of other noncurrent assets and liabilities at Rosewater as of June 30, 2026.
GenCo VIE. In October 2025, a 19.9% equity interest in NiSource's wholly owned subsidiary, Generation Holdings II, the sole owner of GenCo, was issued to BIP Orion Holdco L.P. and BIP Orion Holdco II L.P., (collectively, “Blackstone Investor”), in exchange for $35.2 million in cash contributions to Generation Holdings II through the Generation Holdings II LLC Agreement. Generation Holdings II is considered a VIE as it passes the variability of its operating results through to its shareholders (Generation Holdings I and Blackstone Investor) and has insufficient equity to finance its activities without additional subordinated financial support. The sole purpose of the VIE is to own and operate GenCo which will acquire and build generation assets and provide capacity and electricity to support data center customers. Generation Holdings II and its wholly owned subsidiary, GenCo, is a consolidated VIE, as we have the power to direct the significant decision-making activities that most impact the ongoing operations and economic performance of the entity (i.e., we are the primary beneficiary) including business development and operating decisions. See Note 4 to the Company’s Consolidated Financial Statements in the Annual Report on Form 10-K for the year ended December 31, 2025, for additional details on the Generation Holdings II LLC Agreement.
During the three and six months ended June 30, 2026, we received $39.8 million and $47.8 million in contributions, respectively, and we made zero distributions during the three and six months ended June 30, 2026, respectively, to our Generation Holdings II minority interest holders based on their relative ownership percentages. There were no contributions received or distributions made during the three and six months ended June 30, 2025.

Our Condensed Consolidated Balance Sheets (unaudited) included the following assets and liabilities associated with the GenCo VIE:
(in millions)June 30, 2026December 31, 2025
Net Property, Plant and Equipment$530.1 $39.7 
Current assets174.3 62.5 
Other assets213.9 305.4 
Regulatory assets10.0 — 
Total assets(1)
928.3 407.6 
Current liabilities322.5 40.8 
Total liabilities(1)
$322.5 $40.8 
(1)The assets of each VIE represent assets of a consolidated VIE that can be used only to settle obligations of the respective consolidated VIE. The creditors of the liabilities of the VIEs do not have recourse to the general credit of the primary beneficiary.
Voting Interest Entities. We retain a controlling financial interest in NIPSCO Holdings II and its subsidiaries and consolidate their financial results. See Note 4 to the Company’s Consolidated Financial Statements in the Annual Report on Form 10-K for the year ended December 31, 2025, for additional details on the Amended NIPSCO Holdings II LLC Agreement. The following table provides information about the contributions from and distributions to our NIPSCO minority interest holders included in our Condensed Statements of Consolidated Cash Flows (unaudited) and Condensed Statements of Consolidated Equity (unaudited).
  
Three Months Ended
June 30,		Six Months Ended
June 30,
(in millions)
2026202520262025
Contributions from NIPSCO minority interest holders$51.2 $99.5 $76.7 $134.3 
Distributions to NIPSCO minority interest holders
27.1 26.9 47.0 44.4 
v3.26.1
Long-Term Debt
 6 Months Ended
Jun. 30, 2026
Long-Term Debt, Current and Noncurrent [Abstract]  
Long-term Debt Long-Term Debt
In May 2026, we completed the issuance and sale of $500.0 million of 4.75% senior unsecured notes maturing in 2031 and $750.0 million of 5.30% senior unsecured notes maturing in 2036. The issuances resulted in approximately $1.236 billion of total net proceeds after discount and debt issuance costs.
v3.26.1
Short-Term Borrowings
 6 Months Ended
Jun. 30, 2026
Short-Term Debt [Abstract]  
Short-Term Borrowings Short-Term Borrowings
We generate short-term borrowings from our revolving credit facility, commercial paper program, and accounts receivable transfer programs. Each of these borrowing sources is described further below.
Revolving Credit Facility. We maintain a revolving credit facility to fund ongoing working capital requirements, including the provision of liquidity support for our commercial paper program, the issuance of letters of credit and general corporate purposes. Our revolving credit facility has a facility limit of $2.50 billion and is comprised of a syndicate of banks. We had no outstanding borrowings under this facility as of June 30, 2026 and December 31, 2025, respectively.
Commercial Paper Program. Our commercial paper program has a limit of $2.50 billion. We had $692.0 million and $736.0 million of commercial paper outstanding with weighted-average interest rates of 4.00% and 3.92% as of June 30, 2026 and December 31, 2025, respectively.
Accounts Receivable Transfer Programs. Columbia of Ohio, NIPSCO, and Columbia of Pennsylvania each maintain a receivables agreement whereby they transfer their customer accounts receivables to third-party financial institutions through consolidated special purpose entities. The three agreements expire between August 2026 and April 2027 and may be further extended if mutually agreed to by the parties thereto.
All receivables transferred to third parties are valued at face value, which approximates fair value due to their short-term nature. The amount of the undivided percentage ownership interest in the accounts receivables transferred is determined in part by required loss reserves under the agreements.
Transfers of accounts receivable are accounted for as secured borrowings resulting in the recognition of short-term borrowings on the Condensed Consolidated Balance Sheets (unaudited). As of June 30, 2026, the maximum amount of debt that could be borrowed related to our accounts receivable programs was $245.0 million.
We had no short-term borrowings related to the securitization transactions as of June 30, 2026 and December 31, 2025, respectively.
For the six months ended June 30, 2026 and 2025, no cash flows from financing activities were recorded related to the change in short-term borrowings due to securitization transactions. Columbia of Ohio, NIPSCO and Columbia of Pennsylvania remain responsible for collecting on the receivables securitized, and the receivables cannot be transferred to another party.
Items listed above are presented net in the Condensed Statements of Consolidated Cash Flows (unaudited) as turnover is quick, the amounts are large, and their maturities are less than 90 days.
v3.26.1
Other Commitments And Contingencies
 6 Months Ended
Jun. 30, 2026
Commitments and Contingencies Disclosure [Abstract]  
Commitments and Contingencies Environmental Matters. Our operations are subject to environmental statutes and regulations related to air quality, water quality, hazardous waste and solid waste. We believe that we are in substantial compliance with the environmental regulations currently applicable to our operations.
It is management's continued intent to address environmental issues in cooperation with regulatory authorities in such a manner as to achieve mutually acceptable compliance plans. However, there can be no assurance that fines and penalties will not be incurred. Management expects a majority of environmental assessment and remediation costs and asset retirement costs, further described below, to be recoverable through rates.
As of June 30, 2026 and December 31, 2025, we had recorded a liability of $80.2 million and $82.6 million, respectively, to cover environmental remediation at various sites. This liability is included in "Other accruals" and "Other noncurrent liabilities and deferred credits" in the Condensed Consolidated Balance Sheets (unaudited). We recognize costs associated with environmental remediation obligations when the incurrence of such costs is probable and the amounts can be reasonably estimated. The original estimates for remediation activities may differ materially from the amount ultimately expended. The actual future expenditures depend on many factors, including laws and regulations, the nature and extent of impact and the method of remediation. These expenditures are not currently estimable at some sites. We periodically adjust our liability as information is collected and estimates become more refined.
CERCLA. Our subsidiaries are potentially responsible parties at waste disposal sites under CERCLA and similar state laws. Under CERCLA, each potentially responsible party can be held jointly, severally and strictly liable for the remediation costs as the EPA, or state, can allow the parties to pay for remedial action or perform remedial action themselves and request reimbursement from the potentially responsible parties. Our affiliates have retained CERCLA environmental liabilities, including remediation liabilities, associated with certain current and former operations. At this time, we cannot estimate the full cost of remediating properties that have not yet been investigated, but it is possible that the future costs could be material to the Condensed Consolidated Financial Statements (unaudited).
MGP. We maintain a program to identify and investigate former MGP sites where our subsidiaries or predecessors may have liability. The program has identified 36 such sites where liability is probable. Remedial actions at many of these sites are being overseen by state or federal environmental agencies through consent agreements or voluntary remediation agreements.
We utilize a probabilistic model to estimate our future remediation costs related to MGP sites. The model was prepared with the assistance of a third party and incorporates our experience and general industry experience with remediating MGP sites. We perform an annual update of the model in the second quarter each year. No material changes to the estimated future remediation costs were identified during the update completed as of June 30, 2026. Our total estimated liability related to the facilities subject to remediation was $72.6 million and $75.5 million at June 30, 2026 and December 31, 2025, respectively. The liability represents our best estimate of the probable cost to remediate the MGP sites. Remediation costs are estimated based on the best available information, applicable remediation standards at the balance sheet date and experience with similar facilities.
CCRs. NIPSCO continues to meet the compliance requirements established by the EPA for the regulation of CCRs. The CCR rule requirements currently in effect required revisions to previously recorded legal obligations associated with the retirement of certain NIPSCO facilities. The actual asset retirement costs related to the CCR rule may vary substantially from the estimates used to record the increased asset retirement obligation due to the uncertainty about the requirements that will be established by environmental authorities, compliance strategies that will be used, and the preliminary nature of available data used to estimate costs. As allowed by the rule, NIPSCO will continue to collect data over time to determine the specific compliance solutions and associated costs and, as a result, the actual costs may vary.

In May 2024, the EPA finalized changes to the current CCR regulations ("Legacy CCR Rule"), which address inactive surface impoundments at inactive facilities, referred to as legacy impoundments, and CCR management units ("CCRMUs") at inactive and active facilities. The rule largely requires these newly regulated units to conform to existing requirements, such as groundwater monitoring, closure requirements, and post-closure care. NIPSCO continues to assess whether existing legal obligations associated with the retirement of certain facilities must be revised and to estimate probable additional required asset retirement costs. NIPSCO expects to receive recovery of any such costs through existing and future depreciation rates.
Other Matters.
EPC Agreements. GenCo has entered into certain EPC contracts to construct generation capacity assets to support our data center strategy, requiring payments at specified periods. In certain instances, we may terminate for convenience the EPC Contracts and pay certain incurred project costs and termination fees.
Pool Resource Asset Agreements. As of June 30, 2026, GenCo executed two fixed price ESA contracts to support the contracted customer demand, which are contingent on regulatory approval (such approval being the responsibility of the respective developers). GenCo has committed approximately $658.7 million under these ESAs over 15 years; however, GenCo has exercised an option and intends to convert one of these ESAs, which relates to a battery storage project (the “Tipton BESS Project”) with 167 MW nameplate capacity that is expected to be completed in 2028, to a BTA (the “Tipton BTA”).
GenCo also entered into a battery e-storage supply agreement of which approximately $122.7 million is considered a noncancelable commitment as of June 30, 2026. We have provided a guarantee related to this supply agreement under which the total guarantee as of June 30, 2026 is $245.4 million.
As of June 30, 2026, NIPSCO entered into market capacity purchase agreements to secure additional capacity for the period 2028 through 2030 for approximately $174.6 million to support the contracted demand load of its data center customers. In April 2026, GenCo entered into a capacity agreement for the period from 2028 through 2040 for approximately $1.1 billion, also to support the contracted demand load of its data center customers. This capacity agreement is subject to regulatory approval.
v3.26.1
Accumulated Other Comprehensive Loss
 6 Months Ended
Jun. 30, 2026
Other Comprehensive Income (Loss), Tax [Abstract]  
Accumulated Other Comprehensive Loss
The following tables display the components of Accumulated Other Comprehensive Loss, net of tax:
(in millions)
Gains and Losses on Securities(1)
Gains and Losses on Cash Flow Hedges(1)
Pension and OPEB Items(1)
Accumulated
Other
Comprehensive
Loss(1)
Balance as of March 31, 2026$(1.1)$(13.7)$5.6 $(9.2)
Other comprehensive income (loss) before reclassifications0.6 — (1.1)(0.5)
Amounts reclassified from accumulated other comprehensive loss0.1 (0.1)0.2 0.2 
Net current-period other comprehensive income (loss)
0.7 (0.1)(0.9)(0.3)
Balance as of June 30, 2026$(0.4)$(13.8)$4.7 $(9.5)
(1)All amounts are net of tax. Amounts in parentheses indicate debits.
(in millions)
Gains and Losses on Securities(1)
Gains and Losses on Cash Flow Hedges(1)
Pension and OPEB Items(1)
Accumulated
Other
Comprehensive
Loss(1)
Balance as of December 31, 2025
$0.1 $(13.6)$7.3 $(6.2)
Other comprehensive loss before reclassifications(0.6)— (2.9)(3.5)
Amounts reclassified from accumulated other comprehensive loss0.1 (0.2)0.3 0.2 
Net current-period other comprehensive income (loss)
(0.5)(0.2)(2.6)(3.3)
Balance as of June 30, 2026$(0.4)$(13.8)$4.7 $(9.5)
(1)All amounts are net of tax. Amounts in parentheses indicate debits.
(in millions)
Gains and Losses on Securities(1)
Gains and Losses on Cash Flow Hedges(1)
Pension and OPEB Items(1)
Accumulated
Other
Comprehensive
Loss(1)
Balance as of March 31, 2025$(3.2)$(13.3)$(12.7)$(29.2)
Other comprehensive income (loss) before reclassifications1.0 — (0.1)0.9 
Amounts reclassified from accumulated other comprehensive loss— (0.1)0.2 0.1 
Net current-period other comprehensive income (loss)1.0 (0.1)0.1 1.0 
Balance as of June 30, 2025$(2.2)$(13.4)$(12.6)$(28.2)
(1)All amounts are net of tax. Amounts in parentheses indicate debits.
(in millions)
Gains and Losses on Securities(1)
Gains and Losses on Cash Flow Hedges(1)
Pension and OPEB Items(1)
Accumulated
Other
Comprehensive
Loss(1)
Balance as of December 31, 2024
$(4.0)$(13.2)$(13.2)$(30.4)
Other comprehensive income before reclassifications1.8 — 0.2 2.0 
Amounts reclassified from accumulated other comprehensive loss— (0.2)0.4 0.2 
Net current-period other comprehensive income (loss)1.8 (0.2)0.6 2.2 
Balance as of June 30, 2025
$(2.2)$(13.4)$(12.6)$(28.2)
(1)All amounts are net of tax. Amounts in parentheses indicate debits.
v3.26.1
Other, Net
 6 Months Ended
Jun. 30, 2026
Other, Net [Abstract]  
Other, Net Other, Net
The following table displays the components of Other, Net included on the Condensed Statements of Consolidated Income (unaudited):
Three Months Ended
June 30,		Six Months Ended
June 30,
(in millions)2026202520262025
Interest income$1.6 $1.5 $6.3 $3.5 
AFUDC equity14.6 8.6 24.4 17.8 
Pension and other postretirement non-service benefit (cost)
2.2 (1.6)4.4 (5.4)
Tax penalty— (8.1)— (9.2)
Miscellaneous
(0.2)0.1 (2.5)(0.4)
Total Other, net$18.2 $0.5 $32.6 $6.3 
v3.26.1
Business Segment Information
 6 Months Ended
Jun. 30, 2026
Segment Reporting [Abstract]  
Business Segment Information Business Segment Information
Our reportable segments reflect the manner in which our business is managed and our resources are allocated. Our operations are divided into two primary reportable segments, the Columbia Operations and the NIPSCO Operations segments. Columbia Operations aggregates the results of the fully regulated and wholly owned subsidiaries of NiSource Gas Distribution Group, Inc. (a holding company that owns Columbia of Kentucky, Columbia of Maryland, Columbia of Ohio, Columbia of Pennsylvania, and Columbia of Virginia). Each Columbia distribution company is an operating segment which we aggregate to form the Columbia Operations reportable segment. NIPSCO Operations includes the results of NIPSCO Holdings I and its majority-owned subsidiaries, including NIPSCO, which has regulated gas and electric operations in northern Indiana.

The remainder of our operations, which are not significant enough on a stand-alone basis to warrant treatment as a reportable segment, are presented as "Corporate and Other" and primarily are comprised of interest expense on holding company debt and unallocated corporate costs and activities, as well as new business development costs associated with GenCo. Refer to Note 3, "Revenue Recognition," for additional information on our segments and their sources of revenues. The following table provides information about our reportable segments. We use operating income as the primary measurement of performance for each of the reportable segments and make decisions on financing, dividends and taxes at the corporate level on a consolidated basis. We provide this measure to our CODM, the CEO, who utilizes it to assess performance and allocation of resources at the operating segment level based on budget-to-actual and actual-to-actual variances. Segment revenues include intersegment sales to affiliated subsidiaries, which are eliminated in consolidation. Affiliated sales are recognized on the basis of prevailing market, regulated prices or at levels provided for under contractual agreements. Operating income is derived from revenues and expenses directly associated with each segment.


Three Months Ended June 30, 2026
(in millions)
Columbia Operations
NIPSCO Operations
Total of Reportable Segments
Operating Revenues
External Revenue
$597.0 $743.9 $1,340.9 
Intersegment Revenue
3.5 0.3 3.8 
Total Operating Revenue$600.5 $744.2 $1,344.7 
Cost of energy
80.8 111.8 192.6 
O&M
225.2 270.4 495.6 
Depreciation
131.4 222.2 353.6 
Total other taxes
59.819.479.2 
Operating Income$103.3 $120.4 $223.7 
Three Months Ended June 30, 2025
(in millions)Columbia OperationsNIPSCO OperationsTotal of Reportable Segments
Operating Revenues
External revenue$601.2 $680.6 $1,281.8 
Intersegment revenue3.5 0.2 3.7 
Total Operating Revenue604.7 680.8 1,285.5 
Cost of energy
110.4 151.4 261.8 
O&M
207.7 211.0 418.7 
Depreciation
111.7 165.9 277.6 
Total other taxes
52.418.170.5
Other segment items(1)
0.3 0.4 0.7 
Operating Income$122.2 $134.0 $256.2 
(1)Other segment items consists of Loss on Sale or Impairment of Assets and other segment income or expenses deemed insignificant which are used to reach our measurement of segment profit or loss, Operating Income.

Six Months Ended June 30, 2026
(in millions)
Columbia Operations
NIPSCO Operations
Total of Reportable Segments
Operating Revenues
External revenue$1,920.2 $1,782.4 $3,702.6 
Intersegment revenue6.9 0.6 7.5 
Total Operating Revenue$1,927.1 $1,783.0 $3,710.1 
Cost of energy
464.7 397.1 861.8 
O&M
503.6 491.8 995.4 
Depreciation
252.3 384.9 637.2 
Total other taxes
130.940.3171.2 
Operating Income$575.6 $468.9 $1,044.5 
Six Months Ended June 30, 2025
(in millions)Columbia OperationsNIPSCO OperationsTotal of Reportable Segments
Operating Revenues
External revenue$1,841.8 $1,622.0 $3,463.8 
Intersegment revenue6.7 0.5 7.2 
Total Operating Revenue1,848.5 1,622.5 3,471.0 
Cost of energy
490.2 419.1 909.3 
O&M
450.7 413.0 863.7 
Depreciation
219.9 307.2 527.1 
Total other taxes
119.436.6156.0
Other segment items(1)
0.3 0.7 1.0 
Operating Income$568.0 $445.9 $1,013.9 
(1)Other segment items consists of Loss on Sale or Impairment of Assets and other segment income or expenses deemed insignificant which are used to reach our measurement of segment profit or loss, Operating Income.
The following table provides information about the assets of our reportable segments included in the Condensed Consolidated Balance Sheets (unaudited):
(in millions)June 30,
2026		December 31,
2025
Assets
Columbia Operations
$16,258.5 $15,903.7 
NIPSCO Operations
19,066.4 18,126.7 
Corporate and Other
2,218.7 1,828.3 
Consolidated Assets
$37,543.6 $35,858.7 

To reconcile the segment tables above to consolidated NiSource:
Three Months Ended June 30, 2026
(in millions)
Total Reportable Segments
Corporate and Other
Eliminations
Consolidated NiSource
Total Operating Revenue
$1,344.7 $163.4 $(165.7)$1,342.4 
Operating Income
223.7 4.4 — 228.1 

Three Months Ended June 30, 2025
(in millions)Total Reportable SegmentsCorporate and OtherEliminationsConsolidated NiSource
Total Operating Revenue$1,285.5 $144.6 $(147.1)$1,283.0 
Operating Income256.2 6.7 — 262.9 
v3.26.1
Supplemental Disclosures of Cash Flow Information
 6 Months Ended
Jun. 30, 2026
Supplemental Cash Flow Elements [Abstract]  
Supplemental Disclosures of Cash Flow Information Supplemental Disclosures of Cash Flow Information
The following table displays the components of Working Capital on the Condensed Statements of Consolidated Cash Flows (unaudited):
Six Months Ended
June 30,
(in millions)20262025
Accounts receivable
$343.5 $185.6 
Income tax receivable
11.8 — 
Gas storage and other inventories
60.6 20.9 
Accounts payable
(238.9)(146.9)
Customer deposits and credits
(119.5)(108.9)
Taxes accrued
21.0 (0.7)
Interest accrued
35.0 20.5 
Exchange gas receivable/payable
(215.6)73.8 
Other accruals
(20.8)(17.6)
Prepayments and other current assets
(116.5)(28.4)
Accrued compensation and employee benefits
(32.6)(63.1)
Total change in working capital
$(272.0)$(64.8)
Six Months Ended
June 30,
(in millions)
20262025
Non-cash transactions:
Capital expenditures included in current liabilities$678.8 $426.6 
Advance deposits transferred to capital expenditures
108.6 — 
Dividends declared but not paid148.0 135.1 
v3.26.1
Insider Trading Arrangements - Shawn Anderson [Member]
 3 Months Ended
Jun. 30, 2026
shares
Trading Arrangements, by Individual  
Name Shawn Anderson
Title Executive Vice President, Chief Financial Officer
Aggregate Available 13,000
v3.26.1
Accounting Changes and Error Corrections (Policies)
 6 Months Ended
Jun. 30, 2026
Accounting Changes and Error Corrections [Abstract]  
New Accounting Pronouncements, Policy
Recently Issued Accounting Pronouncements
In May 2026, the FASB issued ASU 2026‑02, Environmental Credits and Environmental Credit Obligations (Topic 818), which establishes comprehensive guidance for the recognition, measurement, presentation, and disclosure of environmental credits and environmental credit obligations. The ASU requires entities to recognize environmental credit assets when it is probable that the credits will be used, transferred, or otherwise realized and to recognize liabilities for environmental credit obligations when events occur on or before the reporting date which result in an environmental credit obligation. The ASU stipulates that measurement is based on either the cost of credits held or the fair value of credits needed to settle the obligation. The amendments are effective for fiscal years beginning after December 15, 2027, including interim periods within those fiscal years, with early adoption permitted. We are currently evaluating the impact this amendment will have on our consolidated financial statements.

In September 2025, the FASB issued ASU 2025-06, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Targeted Improvements to the Accounting for Internal-Use Software. We are currently evaluating the impacts this amendment will have on our internal-use software capitalization policy. See Note 2 to the Company’s Consolidated Financial Statements in the Annual Report on Form 10-K for the year ended December 31, 2025, for a discussion of the impact of this ASU.

In November 2024, the FASB issued ASU 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40). We are currently evaluating the impacts this amendment will have on our required disclosures. See Note 2 to the Company’s Consolidated Financial Statements in the Annual Report on Form 10-K for the year ended December 31, 2025, for a discussion of the impact of this ASU.
v3.26.1
Revenue Recognition (Tables)
 6 Months Ended
Jun. 30, 2026
Revenue from Contract with Customer [Abstract]  
Disaggregation of Revenue
The tables below reconcile revenue disaggregation by customer class to segment revenue, as well as to revenues reflected on the Condensed Statements of Consolidated Income (unaudited):
Three months ended June 30, 2026
(in millions)
Columbia OperationsNIPSCO OperationsCorporate and OtherTotal
Gas Distribution
Residential$399.9 $102.2 $— $502.1 
Commercial124.6 41.4 — 166.0 
Industrial40.3 21.0 — 61.3 
Off-system11.5 — — 11.5 
Miscellaneous(1)
8.5 3.0 — 11.5 
Subtotal$584.8 $167.6 $— $752.4 
Electric Generation and Power Delivery
Residential— 183.1 — 183.1 
Commercial— 181.7 — 181.7 
Industrial— 159.2 — 159.2 
Wholesale— 9.9 — 9.9 
Public Authority— 3.7 — 3.7 
Miscellaneous(1)
— (0.5)— (0.5)
Subtotal $— $537.1 $— $537.1 
Total Customer Revenues(2)
584.8 704.7 — 1,289.5 
Other Revenues(3)
12.2 39.2 1.5 52.9 
Total Operating Revenues$597.0 $743.9 $1.5 $1,342.4 
(1)Amounts included in Columbia Operations primarily relate to earnings share mechanisms, late fees, and wholesale revenues. Amounts included in NIPSCO Operations primarily relate to late fees, property rentals, transmission revenue, and offsetting regulatory program deferrals. (2)Customer revenue amounts exclude intersegment revenues. See Note 17, "Business Segment Information," for discussion of intersegment revenues.
(3)Amounts included in Columbia Operations primarily relate to alternative revenue programs including weather normalization adjustment mechanisms. Amounts included in NIPSCO Operations primarily relate to alternative revenue programs including weather normalization adjustment mechanisms, MISO multi-value projects and revenue from FERC jurisdictional transmission assets. Amounts included in Corporate and Other primarily relate to products and services revenue.
Three months ended June 30, 2025
(in millions)
Columbia Operations
NIPSCO Operations
Corporate and OtherTotal
Gas Distribution
Residential$397.0 $114.2 $— $511.2 
Commercial126.2 45.5 — 171.7 
Industrial37.6 22.6 — 60.2 
Off-system22.8 — — 22.8 
Miscellaneous(1)
8.7 3.3 — 12.0 
Subtotal$592.3 $185.6 $— $777.9 
Electric Generation and Power Delivery
Residential$— $163.9 $— $163.9 
Commercial— 161.0 — 161.0 
Industrial— 133.5 — 133.5 
Wholesale— 11.9 — 11.9 
Miscellaneous(1)
— (1.7)— (1.7)
Subtotal$— $468.6 $— $468.6 
Total Customer Revenues(2)
592.3 654.2 — 1,246.5 
Other Revenues(3)
8.9 26.4 1.2 36.5 
Total Operating Revenues$601.2 $680.6 $1.2 $1,283.0 
(1)Amounts included in Columbia Operations primarily relate to earnings share mechanisms and late fees. Amounts included in NIPSCO Operations primarily relate to late fees and property rentals. (2)Customer revenue amounts exclude intersegment revenues. See Note 17, "Business Segment Information," for discussion of intersegment revenues.
(3)Amounts included in Columbia Operations primarily relate to alternative revenue programs including weather normalization adjustment mechanisms. Amounts included in NIPSCO Operations primarily relate to alternative revenue programs including weather normalization adjustment mechanisms, MISO multi-value projects and revenue from FERC jurisdictional transmission assets. Amounts included in Corporate and Other primarily relate to products and services revenue.
Six months ended June 30, 2026
(in millions)
Columbia OperationsNIPSCO OperationsCorporate and OtherTotal
Gas Distribution
Residential$1,309.1 $420.8 $— $1,729.9 
Commercial455.6 157.0 — 612.6 
Industrial97.7 55.1 — 152.8 
Off-system28.3 — — 28.3 
Miscellaneous(1)
22.7 6.1 — 28.8 
Subtotal$1,913.4 $639.0 $— $2,552.4 
Electric Generation and Power Delivery
Residential$— $359.9 $— $359.9 
Commercial— 353.8 — 353.8 
Industrial— 314.7 — 314.7 
Wholesale— 18.4 — 18.4 
Public Authority— 8.0 — 8.0 
Miscellaneous(1)
— 4.6 — 4.6 
Subtotal$— $1,059.4 $— $1,059.4 
Total Customer Revenues(2)
1,913.4 1,698.4 — 3,611.8 
Other Revenues(3)
6.8 84.0 2.9 93.7 
Total Operating Revenues$1,920.2 $1,782.4 $2.9 $3,705.5 
(1)Amounts included in Columbia Operations are primarily relate to earnings share mechanisms, late fees, and wholesale revenues. Amounts included in NIPSCO Operations primarily relate to late fees, property rentals, transmission revenue, and offsetting regulatory program deferrals. (2)Customer revenue amounts exclude intersegment revenues. See Note 17, "Business Segment Information," for discussion of intersegment revenues.
(3)Amounts included in Columbia Operations primarily relate to alternative revenue programs including weather normalization adjustment mechanisms. Amounts included in NIPSCO Operations primarily relate to alternative revenue programs including weather adjustment mechanisms, MISO multi-value projects and revenue from FERC jurisdictional transmission assets. Amounts included in Corporate and Other primarily relate to products and services revenue.
Six months ended June 30, 2025
(in millions)
Columbia OperationsNIPSCO OperationsCorporate and OtherTotal
Gas Distribution
Residential$1,248.2 $405.6 $— $1,653.8 
Commercial432.7 148.6 — 581.3 
Industrial85.5 54.0 — 139.5 
Off-system45.1 — — 45.1 
Miscellaneous(1)
20.7 8.0 — 28.7 
Subtotal$1,832.2 $616.2 $— $2,448.4 
Electric Generation and Power Delivery
Residential$— $331.8 $— $331.8 
Commercial— 321.1 — 321.1 
Industrial— 276.1 — 276.1 
Wholesale— 19.5 — 19.5 
Miscellaneous(1)
— (0.9)— (0.9)
Subtotal$— $947.6 $— $947.6 
Total Customer Revenues(2)
1,832.2 1,563.8 — 3,396.0 
Other Revenues(3)
9.6 58.2 2.4 70.2 
Total Operating Revenues$1,841.8 $1,622.0 $2.4 $3,466.2 
(1)Amounts included in Columbia Operations are primarily relate to earnings share mechanisms and late fees. Amounts included in NIPSCO Operations, primarily relate to revenue refunds, public repairs and property rentals. (2)Customer revenue amounts exclude intersegment revenues. See Note 17, "Business Segment Information," for discussion of intersegment revenues.
(3)Amounts included in Columbia Operations primarily relate to weather normalization adjustment mechanisms. Amounts included in NIPSCO Operations primarily relate to MISO multi-value projects and revenue from FERC jurisdictional transmission assets. Amounts included in Corporate and Other primarily relate to products and services revenue.
Customer Accounts Receivable The balances of customer receivables as of June 30, 2026 and December 31, 2025 are presented in the table below. Contract liability balances were $95.0 million and zero as of June 30, 2026 and December 31, 2025, respectively. The increase was primarily attributable to consideration received in advance under a customer arrangement. Additionally, we have not incurred any significant costs to obtain or fulfill contracts.
(in millions)Customer Accounts Receivable, Billed (less reserve)Customer Accounts Receivable, Unbilled (less reserve)
Balance as of December 31, 2025$698.8 $465.2 
Balance as of June 30, 2026$694.5 $118.0 
Accounts Receivable, Allowance for Credit Loss of our allowance for credit losses as of June 30, 2026 and December 31, 2025 are presented in the table below:

(in millions)
Columbia Operations
NIPSCO Operations
Total
Balance as of December 31, 2025$15.6 $25.0 $40.6 
Current period provisions24.4 10.2 34.6 
Write-offs charged against allowance(30.2)(10.2)(40.4)
Recoveries of amounts previously written off4.7 0.7 5.4 
Balance as of June 30, 2026$14.5 $25.7 $40.2 
(in millions)
Columbia Operations
NIPSCO Operations
Total
Balance as of December 31, 2024$9.8 $13.9 $23.7 
Current period provisions42.3 25.0 67.3 
Write-offs charged against allowance(50.8)(15.0)(65.8)
Recoveries of amounts previously written off14.3 1.1 15.4 
Balance as of December 31, 2025$15.6 $25.0 $40.6 
v3.26.1
Earnings Per Share (Tables)
 6 Months Ended
Jun. 30, 2026
Earnings Per Share [Abstract]  
Schedule of Earnings Per Share, Basic and Diluted
The following table presents the calculation of our basic and diluted EPS:
Three Months Ended
June 30,		Six Months Ended
June 30,
(in millions, except per share amounts)2026202520262025
Numerator:
Net Income Available to Common Shareholders
$45.5 $102.2 $556.2 $577.0 
Less: Income allocated to participating securities0.1 0.3 1.2 1.1 
Net Income Available to Common Shareholders - Basic
45.4 101.9 555.0 575.9 
Net Income Available to Common Shareholders - Diluted
$45.4 $101.9 $555.0 $575.9 
Denominator:
Average common shares outstanding - Basic479.7 471.0 479.4 470.6 
Dilutive potential common shares:
Shares contingently issuable under employee stock plans1.1 1.0 1.3 1.2 
Shares restricted under employee stock plans0.1 0.1 0.1 0.5 
ATM forward sale agreements
0.3 — 0.2 
Average Common Shares - Diluted481.2 472.1 481.0 472.3 
Earnings per common share:
Basic$0.10 $0.22 $1.16 $1.22 
Diluted$0.09 $0.22 $1.15 $1.22 
v3.26.1
Risk Management Activities (Tables)
 6 Months Ended
Jun. 30, 2026
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value
Risk management assets and liabilities on our derivatives are presented on the Condensed Consolidated Balance Sheets (unaudited) as shown below:
June 30, 2026December 31, 2025
(in millions)Assets LiabilitiesAssetsLiabilities
Current(1)
Derivatives not designated as hedging instruments$2.9 $3.5 $9.7 $2.1 
Total$2.9 $3.5 $9.7 $2.1 
Noncurrent(2)
Derivatives not designated as hedging instruments$8.7 $10.8 $9.1 $3.8 
Total$8.7 $10.8 $9.1 $3.8 
(1)Current assets and liabilities are presented in "Other current assets" and "Other accruals", respectively, on the Condensed Consolidated Balance Sheets (unaudited).
(2)Noncurrent assets and liabilities are presented in "Deferred charges and other" and "Other noncurrent liabilities", respectively, on the Condensed Consolidated Balance Sheets (unaudited).
Derivative Instruments, Gain (Loss)
The following table summarizes the gains and losses associated with the commodity price risk programs deferred as regulatory assets and liabilities:
(in millions)June 30, 2026December 31, 2025
Regulatory Assets
Losses on commodity price risk programs$20.3 $10.1 
Regulatory Liabilities
Gains on commodity price risk programs$12.2 $19.2 
Our derivative instruments measured at fair value as of June 30, 2026 and December 31, 2025 do not contain any credit-risk-related contingent features.
v3.26.1
Fair Value (Tables)
 6 Months Ended
Jun. 30, 2026
Fair Value Disclosures [Abstract]  
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis
The following tables present financial assets and liabilities measured and recorded at fair value on our Condensed Consolidated Balance Sheets (unaudited) on a recurring basis and their level within the fair value hierarchy as of June 30, 2026 and December 31, 2025. As of June 30, 2026 and December 31, 2025, there were no material transfers between fair value hierarchies. Additionally, there were no changes in the method or significant assumptions used to estimate the fair value of our financial instruments.
Recurring Fair Value Measurements
June 30, 2026 (in millions)
Quoted Prices in
Active Markets
for Identical
Assets
(Level 1)		Significant
Other
Observable
Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)
Balance as of
June 30, 2026
Assets
Risk management assets$— $11.6 $— $11.6 
Available-for-sale debt securities— 163.3 — 163.3 
Equity securities(1)(2)
9.4 — — 9.4 
Total$9.4 $174.9 $— $184.3 
Liabilities
Risk management liabilities$— $14.3 $— $14.3 
Total$— $14.3 $— $14.3 
(1)Equity securities are in a high dividend equity fund and are valued using market prices in active markets. Level 1 instrument valuations are obtained from real-time quotes for transactions in active exchange markets involving identical assets. Equity securities are presented in "Other Investments" on the Condensed Consolidated Balance Sheets (unaudited).
(2)As of June 30, 2026, the investment cost of equity securities measured at fair value was $7.9 million, gross unrealized gains were $1.6 million, and the fair value was $9.4 million.
Recurring Fair Value Measurements
December 31, 2025 (in millions)
Quoted Prices in
Active Markets
for Identical
Assets
(Level 1)		Significant
Other
Observable
Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)
Balance as of
December 31, 2025
Assets
Risk management assets$— $18.8 $— $18.8 
Available-for-sale debt securities— 146.1 — 146.1 
Equity Securities(1)(2)
8.5 — — 8.5 
Total$8.5 $164.9 $— $173.4 
Liabilities
Risk management liabilities$— $5.9 $— $5.9 
Total$— $5.9 $— $5.9 
Debt Securities, Available-for-sale
The amortized cost, gross unrealized gains and losses, allowance for credit losses, and fair value of available-for-sale securities at June 30, 2026 and December 31, 2025 were: 
June 30, 2026 (in millions)
Amortized
Cost		Gross Unrealized Gains
Gross Unrealized Losses(1)
Fair
Value
Available-for-sale debt securities
U.S. Treasury debt securities$10.4 $— $(0.1)$10.3 
Corporate/Other debt securities154.2 1.4 (2.6)153.0 
Total$164.6 $1.4 $(2.7)$163.3 
December 31, 2025 (in millions)
Amortized
Cost		Gross Unrealized Gains
Gross Unrealized Losses(2)
Fair
Value
Available-for-sale debt securities
U.S. Treasury debt securities$9.5 $— $— $9.5 
Corporate/Other debt securities136.3 2.4 (2.1)136.6 
Total$145.8 $2.4 $(2.1)$146.1 
(1)Fair value of U.S. Treasury debt securities and Corporate/Other debt securities in an unrealized loss position without an allowance for credit losses is $8.7 million and $74.2 million, respectively, at June 30, 2026.
(2)Fair value of U.S. Treasury debt securities and Corporate/Other debt securities in an unrealized loss position without an allowance for credit losses is $3.5 million and $40.2 million, respectively, at December 31, 2025.
Carrying Amount And Estimated Fair Values Of Financial Instruments
The carrying amount and estimated fair values of these financial instruments were as follows: 
(in millions)
Carrying
Amount as of
June 30, 2026
Estimated Fair
Value as of
June 30, 2026
Carrying
Amount as of
Dec. 31, 2025
Estimated Fair
Value as of
Dec. 31, 2025
Long-term debt (including current portion)$16,711.0 $16,015.4 $15,477.5 $14,975.3 
v3.26.1
Pension And Other Postretirement Benefits (Tables)
 6 Months Ended
Jun. 30, 2026
Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]  
Components Of The Plans' Net Periodic Benefits Cost
The following table provides the components of the plans' actuarially determined net periodic benefit cost for the three and six months ended June 30, 2026 and 2025:
Pension BenefitsOPEB
Three Months Ended June 30, (in millions)
2026202520262025
Components of Net Periodic Benefit Cost(1)
Service cost$5.2 $4.9 $0.9 $1.0 
Interest cost14.1 16.0 4.6 5.6 
Expected return on assets(22.5)(23.1)(4.2)(4.2)
Amortization of prior service credit— — (1.1)(0.4)
Recognized actuarial loss5.9 6.4 — 0.4 
Total Net Periodic Benefit Cost $2.7 $4.2 $0.2 $2.4 
(1)The service cost component and all non-service cost components of net periodic benefit (income) cost are presented in "Operation and maintenance" and "Other, net," respectively, on the Condensed Statements of Consolidated Income (unaudited).
v3.26.1
Variable Interest Entities (Tables)
 6 Months Ended
Jun. 30, 2026
Variable Interest Entities [Abstract]  
Variable Interest Entities Assets and Liabilities
Our Condensed Consolidated Balance Sheets (unaudited) included the following assets and liabilities associated with the JV VIEs.
(in millions)June 30, 2026December 31, 2025
Net property, plant and equipment
$1,233.9 $1,273.0 
Current assets49.1 27.6 
Total assets(1)
1,283.0 1,300.6 
Current liabilities13.1 16.1 
Asset retirement obligations57.0 55.7 
Finance lease obligations
40.0 40.1 
Total liabilities(1)(2)
$110.1 $111.9 
Contributions/Distributions to/from Noncontrolling Interest The following table provides information about the contributions from and distributions to our NIPSCO minority interest holders included in our Condensed Statements of Consolidated Cash Flows (unaudited) and Condensed Statements of Consolidated Equity (unaudited).
  
Three Months Ended
June 30,		Six Months Ended
June 30,
(in millions)
2026202520262025
Contributions from NIPSCO minority interest holders$51.2 $99.5 $76.7 $134.3 
Distributions to NIPSCO minority interest holders
27.1 26.9 47.0 44.4 
v3.26.1
Accumulated Other Comprehensive Loss (Tables)
 6 Months Ended
Jun. 30, 2026
Other Comprehensive Income (Loss), Tax [Abstract]  
Components Of Accumulated Other Comprehensive Loss
The following tables display the components of Accumulated Other Comprehensive Loss, net of tax:
(in millions)
Gains and Losses on Securities(1)
Gains and Losses on Cash Flow Hedges(1)
Pension and OPEB Items(1)
Accumulated
Other
Comprehensive
Loss(1)
Balance as of March 31, 2026$(1.1)$(13.7)$5.6 $(9.2)
Other comprehensive income (loss) before reclassifications0.6 — (1.1)(0.5)
Amounts reclassified from accumulated other comprehensive loss0.1 (0.1)0.2 0.2 
Net current-period other comprehensive income (loss)
0.7 (0.1)(0.9)(0.3)
Balance as of June 30, 2026$(0.4)$(13.8)$4.7 $(9.5)
(1)All amounts are net of tax. Amounts in parentheses indicate debits.
(in millions)
Gains and Losses on Securities(1)
Gains and Losses on Cash Flow Hedges(1)
Pension and OPEB Items(1)
Accumulated
Other
Comprehensive
Loss(1)
Balance as of December 31, 2025
$0.1 $(13.6)$7.3 $(6.2)
Other comprehensive loss before reclassifications(0.6)— (2.9)(3.5)
Amounts reclassified from accumulated other comprehensive loss0.1 (0.2)0.3 0.2 
Net current-period other comprehensive income (loss)
(0.5)(0.2)(2.6)(3.3)
Balance as of June 30, 2026$(0.4)$(13.8)$4.7 $(9.5)
(1)All amounts are net of tax. Amounts in parentheses indicate debits.
(in millions)
Gains and Losses on Securities(1)
Gains and Losses on Cash Flow Hedges(1)
Pension and OPEB Items(1)
Accumulated
Other
Comprehensive
Loss(1)
Balance as of March 31, 2025$(3.2)$(13.3)$(12.7)$(29.2)
Other comprehensive income (loss) before reclassifications1.0 — (0.1)0.9 
Amounts reclassified from accumulated other comprehensive loss— (0.1)0.2 0.1 
Net current-period other comprehensive income (loss)1.0 (0.1)0.1 1.0 
Balance as of June 30, 2025$(2.2)$(13.4)$(12.6)$(28.2)
(1)All amounts are net of tax. Amounts in parentheses indicate debits.
(in millions)
Gains and Losses on Securities(1)
Gains and Losses on Cash Flow Hedges(1)
Pension and OPEB Items(1)
Accumulated
Other
Comprehensive
Loss(1)
Balance as of December 31, 2024
$(4.0)$(13.2)$(13.2)$(30.4)
Other comprehensive income before reclassifications1.8 — 0.2 2.0 
Amounts reclassified from accumulated other comprehensive loss— (0.2)0.4 0.2 
Net current-period other comprehensive income (loss)1.8 (0.2)0.6 2.2 
Balance as of June 30, 2025
$(2.2)$(13.4)$(12.6)$(28.2)
(1)All amounts are net of tax. Amounts in parentheses indicate debits.
v3.26.1
Other, Net (Tables)
 6 Months Ended
Jun. 30, 2026
Other, Net [Abstract]  
Schedule of Other Nonoperating Income (Expense)
The following table displays the components of Other, Net included on the Condensed Statements of Consolidated Income (unaudited):
Three Months Ended
June 30,		Six Months Ended
June 30,
(in millions)2026202520262025
Interest income$1.6 $1.5 $6.3 $3.5 
AFUDC equity14.6 8.6 24.4 17.8 
Pension and other postretirement non-service benefit (cost)
2.2 (1.6)4.4 (5.4)
Tax penalty— (8.1)— (9.2)
Miscellaneous
(0.2)0.1 (2.5)(0.4)
Total Other, net$18.2 $0.5 $32.6 $6.3 
v3.26.1
Business Segment Information (Tables)
 6 Months Ended
Jun. 30, 2026
Segment Reporting [Abstract]  
Schedule Of Operating Income Derived From Revenues And Expenses By Segment
Three Months Ended June 30, 2026
(in millions)
Columbia Operations
NIPSCO Operations
Total of Reportable Segments
Operating Revenues
External Revenue
$597.0 $743.9 $1,340.9 
Intersegment Revenue
3.5 0.3 3.8 
Total Operating Revenue$600.5 $744.2 $1,344.7 
Cost of energy
80.8 111.8 192.6 
O&M
225.2 270.4 495.6 
Depreciation
131.4 222.2 353.6 
Total other taxes
59.819.479.2 
Operating Income$103.3 $120.4 $223.7 
Three Months Ended June 30, 2025
(in millions)Columbia OperationsNIPSCO OperationsTotal of Reportable Segments
Operating Revenues
External revenue$601.2 $680.6 $1,281.8 
Intersegment revenue3.5 0.2 3.7 
Total Operating Revenue604.7 680.8 1,285.5 
Cost of energy
110.4 151.4 261.8 
O&M
207.7 211.0 418.7 
Depreciation
111.7 165.9 277.6 
Total other taxes
52.418.170.5
Other segment items(1)
0.3 0.4 0.7 
Operating Income$122.2 $134.0 $256.2 
(1)Other segment items consists of Loss on Sale or Impairment of Assets and other segment income or expenses deemed insignificant which are used to reach our measurement of segment profit or loss, Operating Income.

Six Months Ended June 30, 2026
(in millions)
Columbia Operations
NIPSCO Operations
Total of Reportable Segments
Operating Revenues
External revenue$1,920.2 $1,782.4 $3,702.6 
Intersegment revenue6.9 0.6 7.5 
Total Operating Revenue$1,927.1 $1,783.0 $3,710.1 
Cost of energy
464.7 397.1 861.8 
O&M
503.6 491.8 995.4 
Depreciation
252.3 384.9 637.2 
Total other taxes
130.940.3171.2 
Operating Income$575.6 $468.9 $1,044.5 
Six Months Ended June 30, 2025
(in millions)Columbia OperationsNIPSCO OperationsTotal of Reportable Segments
Operating Revenues
External revenue$1,841.8 $1,622.0 $3,463.8 
Intersegment revenue6.7 0.5 7.2 
Total Operating Revenue1,848.5 1,622.5 3,471.0 
Cost of energy
490.2 419.1 909.3 
O&M
450.7 413.0 863.7 
Depreciation
219.9 307.2 527.1 
Total other taxes
119.436.6156.0
Other segment items(1)
0.3 0.7 1.0 
Operating Income$568.0 $445.9 $1,013.9 
(1)Other segment items consists of Loss on Sale or Impairment of Assets and other segment income or expenses deemed insignificant which are used to reach our measurement of segment profit or loss, Operating Income.
The following table provides information about the assets of our reportable segments included in the Condensed Consolidated Balance Sheets (unaudited):
(in millions)June 30,
2026		December 31,
2025
Assets
Columbia Operations
$16,258.5 $15,903.7 
NIPSCO Operations
19,066.4 18,126.7 
Corporate and Other
2,218.7 1,828.3 
Consolidated Assets
$37,543.6 $35,858.7 

To reconcile the segment tables above to consolidated NiSource:
Three Months Ended June 30, 2026
(in millions)
Total Reportable Segments
Corporate and Other
Eliminations
Consolidated NiSource
Total Operating Revenue
$1,344.7 $163.4 $(165.7)$1,342.4 
Operating Income
223.7 4.4 — 228.1 

Three Months Ended June 30, 2025
(in millions)Total Reportable SegmentsCorporate and OtherEliminationsConsolidated NiSource
Total Operating Revenue$1,285.5 $144.6 $(147.1)$1,283.0 
Operating Income256.2 6.7 — 262.9 
v3.26.1
Supplemental Disclosures of Cash Flow Information (Tables)
 6 Months Ended
Jun. 30, 2026
Supplemental Cash Flow Elements [Abstract]  
Schedule of Cash Flow, Supplemental Disclosures
The following table displays the components of Working Capital on the Condensed Statements of Consolidated Cash Flows (unaudited):
Six Months Ended
June 30,
(in millions)20262025
Accounts receivable
$343.5 $185.6 
Income tax receivable
11.8 — 
Gas storage and other inventories
60.6 20.9 
Accounts payable
(238.9)(146.9)
Customer deposits and credits
(119.5)(108.9)
Taxes accrued
21.0 (0.7)
Interest accrued
35.0 20.5 
Exchange gas receivable/payable
(215.6)73.8 
Other accruals
(20.8)(17.6)
Prepayments and other current assets
(116.5)(28.4)
Accrued compensation and employee benefits
(32.6)(63.1)
Total change in working capital
$(272.0)$(64.8)
Six Months Ended
June 30,
(in millions)
20262025
Non-cash transactions:
Capital expenditures included in current liabilities$678.8 $426.6 
Advance deposits transferred to capital expenditures
108.6 — 
Dividends declared but not paid148.0 135.1 
v3.26.1
Revenue Recognition (Narrative) (Details) - USD ($)
$ in Millions
 6 Months Ended 9 Months Ended
Jun. 30, 2026
Sep. 30, 2025
Dec. 31, 2025
Dec. 31, 2024
Revenue from Contract with Customer [Abstract]        
Accounts Receivable, Allowance for Credit Loss $ 40.2   $ 40.6 $ 23.7
Current period provisions 34.6 $ 67.3    
Write-offs charged against allowance (40.4) (65.8)    
Recoveries of amounts previously written off $ 5.4 $ 15.4    
v3.26.1
Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Disaggregation of Revenue [Line Items]          
Customer revenues $ 1,289.5 $ 1,246.5 $ 3,611.8 $ 3,396.0  
Other revenues 52.9 36.5 93.7 70.2  
Total Operating Revenues 1,342.4 1,283.0 3,705.5 3,466.2  
Operating Segments          
Disaggregation of Revenue [Line Items]          
Total Operating Revenues 1,344.7 1,285.5 3,710.1 3,471.0  
Operating Segments | Nonrelated Party          
Disaggregation of Revenue [Line Items]          
Total Operating Revenues 1,340.9 1,281.8 3,702.6 3,463.8  
NIPSCO Electric Generation          
Disaggregation of Revenue [Line Items]          
Customer revenues       947.6  
NiSource Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues 752.4 777.9 2,552.4 2,448.4  
NiSource Electric Generation and Power Delivery          
Disaggregation of Revenue [Line Items]          
Customer revenues 537.1 468.6 1,059.4    
Corporate and Other          
Disaggregation of Revenue [Line Items]          
Customer revenues 0.0 0.0 0.0 0.0  
Other revenues 1.5 1.2 2.9 2.4  
Corporate and Other | Unaffiliated          
Disaggregation of Revenue [Line Items]          
Revenues 1.5 1.2 2.9 2.4  
NIPSCO Operations          
Disaggregation of Revenue [Line Items]          
Customer revenues 704.7 654.2   1,563.8  
Other revenues 39.2 26.4 84.0 58.2  
Total Operating Revenues 743.9 680.6      
NIPSCO Operations | Operating Segments          
Disaggregation of Revenue [Line Items]          
Total Operating Revenues 744.2 680.8 1,783.0 1,622.5  
NIPSCO Operations | Operating Segments | Nonrelated Party          
Disaggregation of Revenue [Line Items]          
Total Operating Revenues 743.9 680.6 1,782.4    
NIPSCO Operations | Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues 167.6 185.6 639.0 616.2  
NIPSCO Operations | NIPSCO Electric Generation          
Disaggregation of Revenue [Line Items]          
Customer revenues 537.1 468.6   947.6  
NIPSCO Operations | Unaffiliated          
Disaggregation of Revenue [Line Items]          
Revenues       1,622.0  
Columbia Operations          
Disaggregation of Revenue [Line Items]          
Customer revenues 584.8 592.3 1,913.4 1,832.2  
Other revenues 12.2 8.9 6.8 9.6  
Columbia Operations | Operating Segments          
Disaggregation of Revenue [Line Items]          
Total Operating Revenues 600.5 604.7 1,927.1 1,848.5  
Columbia Operations | Operating Segments | Nonrelated Party          
Disaggregation of Revenue [Line Items]          
Total Operating Revenues 597.0 601.2 1,920.2    
Columbia Operations | Unaffiliated          
Disaggregation of Revenue [Line Items]          
Revenues     1,920.2 1,841.8  
NIPSCO          
Disaggregation of Revenue [Line Items]          
Customer revenues     1,698.4    
Total Operating Revenues     1,782.4    
Contract with Customer, Contract Asset, Contract Liability, and Receivable [Abstract]          
Contract with Customer, Liability 95.0   95.0   $ 0.0
NIPSCO | NIPSCO Electric Generation          
Disaggregation of Revenue [Line Items]          
Customer revenues     1,059.4    
Residential | NiSource Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues 502.1 511.2 1,729.9 1,653.8  
Residential | NiSource Electric Generation and Power Delivery          
Disaggregation of Revenue [Line Items]          
Customer revenues 183.1 163.9 359.9 331.8  
Residential | Corporate and Other          
Disaggregation of Revenue [Line Items]          
Customer revenues 0.0 0.0 0.0 0.0  
Residential | NIPSCO Operations | Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues 102.2 114.2 420.8 405.6  
Residential | NIPSCO Operations | NIPSCO Electric Generation          
Disaggregation of Revenue [Line Items]          
Customer revenues 183.1 163.9 359.9 331.8  
Residential | Columbia Operations          
Disaggregation of Revenue [Line Items]          
Customer revenues 399.9 397.0 1,309.1 1,248.2  
Commercial | NiSource Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues 166.0 171.7 612.6 581.3  
Commercial | NiSource Electric Generation and Power Delivery          
Disaggregation of Revenue [Line Items]          
Customer revenues 181.7 161.0 353.8 321.1  
Commercial | Corporate and Other          
Disaggregation of Revenue [Line Items]          
Customer revenues 0.0 0.0 0.0 0.0  
Commercial | NIPSCO Operations | Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues 41.4 45.5 157.0 148.6  
Commercial | NIPSCO Operations | NIPSCO Electric Generation          
Disaggregation of Revenue [Line Items]          
Customer revenues 181.7 161.0 353.8 321.1  
Commercial | Columbia Operations          
Disaggregation of Revenue [Line Items]          
Customer revenues 124.6 126.2 455.6 432.7  
Industrial | NiSource Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues 61.3 60.2 152.8 139.5  
Industrial | NiSource Electric Generation and Power Delivery          
Disaggregation of Revenue [Line Items]          
Customer revenues 159.2 133.5 314.7 276.1  
Industrial | Corporate and Other          
Disaggregation of Revenue [Line Items]          
Customer revenues 0.0 0.0 0.0 0.0  
Industrial | NIPSCO Operations | Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues 21.0 22.6 55.1 54.0  
Industrial | NIPSCO Operations | NIPSCO Electric Generation          
Disaggregation of Revenue [Line Items]          
Customer revenues 159.2 133.5 314.7 276.1  
Industrial | Columbia Operations          
Disaggregation of Revenue [Line Items]          
Customer revenues 40.3 37.6 97.7 85.5  
Off-system | NiSource Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues 11.5 22.8 28.3 45.1  
Off-system | Corporate and Other          
Disaggregation of Revenue [Line Items]          
Customer revenues 0.0 0.0 0.0 0.0  
Off-system | NIPSCO Operations | Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues 0.0 0.0 0.0 0.0  
Off-system | Columbia Operations          
Disaggregation of Revenue [Line Items]          
Customer revenues 11.5 22.8 28.3 45.1  
Miscellaneous | NiSource Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues 11.5 12.0 28.8 28.7  
Miscellaneous | NiSource Electric Generation and Power Delivery          
Disaggregation of Revenue [Line Items]          
Customer revenues (0.5) (1.7) 4.6    
Miscellaneous | Corporate and Other          
Disaggregation of Revenue [Line Items]          
Customer revenues 0.0 0.0 0.0 0.0  
Miscellaneous | NIPSCO Operations | Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues 3.0 3.3 6.1 8.0  
Miscellaneous | NIPSCO Operations | NIPSCO Electric Generation          
Disaggregation of Revenue [Line Items]          
Customer revenues (0.5) (1.7) 4.6 (0.9)  
Miscellaneous | Columbia Operations          
Disaggregation of Revenue [Line Items]          
Customer revenues 8.5 8.7 22.7 20.7  
Wholesale | NiSource Electric Generation and Power Delivery          
Disaggregation of Revenue [Line Items]          
Customer revenues 9.9 11.9 18.4 19.5  
Wholesale | NIPSCO Operations | NIPSCO Electric Generation          
Disaggregation of Revenue [Line Items]          
Customer revenues 9.9 $ 11.9 18.4 19.5  
Public Authority          
Disaggregation of Revenue [Line Items]          
Customer revenues 3.7   8.0 $ (0.9)  
Public Authority | NIPSCO Operations | NIPSCO Electric Generation          
Disaggregation of Revenue [Line Items]          
Customer revenues $ 3.7   $ 8.0    
v3.26.1
Revenue Recognition (Customer Accounts Receivable) (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Revenue from Contract with Customer [Abstract]    
Customer Accounts Receivable, Billed (Less Reserve) $ 694.5 $ 698.8
Customer Accounts Receivable, Unbilled (Less Reserve) $ 118.0 $ 465.2
v3.26.1
Revenue Recognition Revenue Recognition (Allowance for Credit Losses) (Details) - USD ($)
$ in Millions
 6 Months Ended 9 Months Ended
Jun. 30, 2026
Sep. 30, 2025
Dec. 31, 2025
Dec. 31, 2024
Accounts Receivable Allowance For Credit Loss [Line Items]        
Accounts Receivable, Allowance for Credit Loss $ 40.2   $ 40.6 $ 23.7
Current period provisions 34.6 $ 67.3    
Write-offs charged against allowance 40.4 65.8    
Recoveries of amounts previously written off 5.4 15.4    
Columbia Operations        
Accounts Receivable Allowance For Credit Loss [Line Items]        
Accounts Receivable, Allowance for Credit Loss 14.5   15.6 9.8
Current period provisions 24.4 42.3    
Write-offs charged against allowance 30.2 50.8    
Recoveries of amounts previously written off 4.7 14.3    
NIPSCO Operations        
Accounts Receivable Allowance For Credit Loss [Line Items]        
Accounts Receivable, Allowance for Credit Loss 25.7   $ 25.0 $ 13.9
Current period provisions 10.2 25.0    
Write-offs charged against allowance 10.2 15.0    
Recoveries of amounts previously written off $ 0.7 $ 1.1    
v3.26.1
Earnings Per Share (Schedule of Earnings Per Share, Basic and Diluted) (Details) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Numerator        
Net Income Available to Common Shareholders $ 45.5 $ 102.2 $ 556.2 $ 577.0
Undistributed Earnings (Loss) Allocated to Participating Securities, Basic 0.1 0.3 1.2 1.1
Net Income Available to Common Shareholders - Basic Excluding Participating Securities 45.4 101.9 555.0 575.9
Net Income Available to Common Shareholders - Diluted $ 45.4 $ 101.9 $ 555.0 $ 575.9
Denominator        
Basic Average Common Shares Outstanding 479.7 471.0 479.4 470.6
Dilutive potential common shares        
Shares contingently issuable under employee stock plans 1.1 1.0 1.3 1.2
Shares restricted under stock plans 0.1 0.1 0.1 0.5
ATM forward sale agreements 0.3 0.0 0.2
Diluted Average Common Shares 481.2 472.1 481.0 472.3
Basic Earnings Per Share $ 0.10 $ 0.22 $ 1.16 $ 1.22
Diluted Earnings Per Share $ 0.09 $ 0.22 $ 1.15 $ 1.22
v3.26.1
Equity (Narrative) (Details) - USD ($)
$ / shares in Units, $ in Millions
 1 Months Ended 3 Months Ended 6 Months Ended
Feb. 22, 2024
Jun. 30, 2026
Feb. 28, 2026
Oct. 31, 2025
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share   $ 46.47 $ 45.63 $ 41.84        
Customer revenues         $ 1,289.5 $ 1,246.5 $ 3,611.8 $ 3,396.0
Preferred Stock, Redemption Amount             3.6  
Corporate and Other                
Customer revenues         $ 0.0 $ 0.0 $ 0.0 0.0
Forward Oct 25                
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share             $ 41.72  
Forward February 26                
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share             45.46  
Forward June 26                
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share             $ 46.10  
Pension Plan                
Defined Benefit Plan, Plan Assets, Contributions by Employer             $ 2.6 1.0
Other Postretirement Benefit Plan                
Defined Benefit Plan, Plan Assets, Contributions by Employer             11.1 $ 10.5
At The Market Program                
Common Stock Aggregate Sale Price $ 1,500.0              
ATM Program Equity Remaining Available for Issuance             1,150.0  
Forward Oct 25                
Common Stock Aggregate Sale Price             99.7  
Forward Contract Indexed to Issuer's Equity, Shares       2,390,057        
Forward February 26                
Common Stock Aggregate Sale Price             100.0  
Forward Contract Indexed to Issuer's Equity, Shares     2,200,000          
Retained Deficit                
Preferred Stock, Redemption Amount             (3.6)  
Forward June 26                
Common Stock Aggregate Sale Price             $ 99.2  
Forward Contract Indexed to Issuer's Equity, Shares     2,151,874          
v3.26.1
Equity Schedule of Stock by Class - Preferred (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Class of Stock [Line Items]    
Shares outstanding $ 9,574.6 $ 9,450.1
v3.26.1
Regulatory Matters (Narrative) (Details)
$ in Millions
 6 Months Ended
Jun. 30, 2026
USD ($)
MW
Dec. 31, 2025
USD ($)
Public Utilities, General Disclosures [Line Items]    
Regulatory Assets, Noncurrent $ 2,360.8 $ 2,225.2
Regulatory Liability, Noncurrent 1,586.2 $ 1,513.3
Sections 205, 202 (c), and 309 Emergency order Cost Recovery 38.0  
Emergency Order 202c    
Public Utilities, General Disclosures [Line Items]    
Regulatory Liability, Noncurrent 33.5  
Emergency Order 202c    
Public Utilities, General Disclosures [Line Items]    
Regulatory Assets, Noncurrent $ 102.2  
Rosewater    
Public Utilities, General Disclosures [Line Items]    
Nameplate Capacity | MW 102  
v3.26.1
Risk Management Activities (Narrative) (Details)
mMDth in Millions, $ in Millions
Jun. 30, 2026
USD ($)
mMDth
Dec. 31, 2025
USD ($)
mMDth
Derivative [Line Items]    
Limit of GCA Volumes 20.00%  
Derivative Asset, Subject to Master Netting Arrangement, after Offset | $ $ 2.7 $ 12.9
Customer annual demand 2000.00%  
Minimum    
Derivative [Line Items]    
Commodity Contract Length 1 year  
Maximum    
Derivative [Line Items]    
Commodity Contract Length 6 years  
Natural Gas    
Derivative [Line Items]    
Derivative, Nonmonetary Notional Amount | mMDth 80.9 83.7
v3.26.1
Risk Management Activities (Schedule of Derivative Instruments in Statement of Financial Position, Fair Value) (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Balance Sheet Location [Axis]: us-gaap:DerivativeAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Risk management assets $ 2.9 $ 9.7
Balance Sheet Location [Axis]: us-gaap:DerivativeAssetsNoncurrent    
Derivatives, Fair Value [Line Items]    
Risk management assets 8.7 9.1
Balance Sheet Location [Axis]: us-gaap:DerivativeLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Risk management liabilities 3.5 2.1
Balance Sheet Location [Axis]: us-gaap:DerivativeLiabilitiesNoncurrent    
Derivatives, Fair Value [Line Items]    
Risk management liabilities 10.8 3.8
Commodity Price Risk Programs | Balance Sheet Location [Axis]: us-gaap:DerivativeAssetsCurrent    
Derivatives, Fair Value [Line Items]    
Risk management assets 2.9 9.7
Commodity Price Risk Programs | Balance Sheet Location [Axis]: us-gaap:DerivativeAssetsNoncurrent    
Derivatives, Fair Value [Line Items]    
Risk management assets 8.7 9.1
Commodity Price Risk Programs | Balance Sheet Location [Axis]: us-gaap:DerivativeLiabilitiesCurrent    
Derivatives, Fair Value [Line Items]    
Risk management liabilities 3.5 2.1
Commodity Price Risk Programs | Balance Sheet Location [Axis]: us-gaap:DerivativeLiabilitiesNoncurrent    
Derivatives, Fair Value [Line Items]    
Risk management liabilities $ 10.8 $ 3.8
v3.26.1
Risk Management Activities (Schedule of Gains (Losses) on Commodity Price Risk Programs) (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Deferred Derivative Gain (Loss)    
Derivative Instruments, Gain (Loss) [Line Items]    
Regulatory Liabilities $ 12.2 $ 19.2
Deferred Derivative Gain (Loss)    
Derivative Instruments, Gain (Loss) [Line Items]    
Regulatory Assets $ 20.3 $ 10.1
v3.26.1
Fair Value (Narrative) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Mar. 31, 2026
Jun. 30, 2026
Dec. 31, 2025
Fair Value Disclosure [Line Items]      
Transfers between Fair Value Hierarchies $ 0.0 $ 0.0  
Fair Value   163.3 $ 146.1
Debt Securities, Available-for-Sale, Realized Gain (Loss)   0.1  
Debt and Equity Securities, FV-NI [Line Items]      
Equity Securities, FV-NI, Cost   7.9 7.9
Debt and Equity Securities, Unrealized Gain (Loss) $ 0.7 1.6  
Equity Securities, FV-NI   9.4 8.5
Net Assets   18.4 17.9
Net Assets   18.4 17.9
U.S. Treasury debt securities      
Fair Value Disclosure [Line Items]      
Fair Value   10.3 9.5
Corporate/Other debt securities      
Fair Value Disclosure [Line Items]      
Available-for-sale Securities, Maturities, Next Twelve Months, Fair Value   10.6  
Fair Value   153.0 $ 136.6
US Treasury Securities      
Fair Value Disclosure [Line Items]      
Fair Value   $ 5.8  
v3.26.1
Fair Value (Fair Value Of Financial Assets And Liabilities Measured On A Recurring Basis) (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Assets    
Available-for-sale, securities $ 163.3 $ 146.1
Equity Securities, FV-NI 9.4 8.5
Total 184.3 173.4
Liabilities    
Total 14.3 5.9
Fair Value, Inputs, Level 1    
Assets    
Risk management assets 0.0 0.0
Available-for-sale, securities 0.0 0.0
Equity Securities, FV-NI 9.4 8.5
Total 9.4 8.5
Liabilities    
Risk management liabilities 0.0 0.0
Total 0.0 0.0
Significant Other Observable Inputs (Level 2)    
Assets    
Risk management assets 11.6 18.8
Available-for-sale, securities 163.3 146.1
Equity Securities, FV-NI 0.0 0.0
Total 174.9 164.9
Liabilities    
Risk management liabilities 14.3 5.9
Total 14.3 5.9
Significant Unobservable Inputs (Level 3)    
Assets    
Risk management assets 0.0 0.0
Available-for-sale, securities 0.0 0.0
Equity Securities, FV-NI 0.0 0.0
Total 0.0 0.0
Liabilities    
Risk management liabilities 0.0 0.0
Total 0.0 0.0
Available-for-sale Securities    
Assets    
Available-for-sale, securities 163.3 146.1
Risk management assets    
Assets    
Risk management assets 11.6 18.8
Liabilities    
Risk management liabilities $ 14.3 $ 5.9
v3.26.1
Fair Value (Available-For-Sale Securities) (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Fair Value Disclosure [Line Items]    
Amortized Cost $ 164.6 $ 145.8
Gross Unrealized Gains 1.4 2.4
Gross Unrealized Losses (2.7) (2.1)
Fair Value 163.3 146.1
U.S. Treasury debt securities    
Fair Value Disclosure [Line Items]    
Amortized Cost 10.4 9.5
Gross Unrealized Gains 0.0 0.0
Gross Unrealized Losses (0.1) 0.0
Fair Value 10.3 9.5
Corporate/Other debt securities    
Fair Value Disclosure [Line Items]    
Amortized Cost 154.2 136.3
Gross Unrealized Gains 1.4 2.4
Gross Unrealized Losses (2.6) (2.1)
Fair Value 153.0 136.6
Debt Securities, Available-for-sale, Unrealized Loss Position 74.2 40.2
US Treasury Securities    
Fair Value Disclosure [Line Items]    
Fair Value 5.8  
Debt Securities, Available-for-sale, Unrealized Loss Position $ 8.7 $ 3.5
v3.26.1
Fair Value (Carrying Amount And Estimated Fair Values Of Financial Instruments) (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Fair Value Disclosures [Abstract]    
Long-term Debt (including current portion), Carrying Amount $ 16,711.0 $ 15,477.5
Long-term debt (including current portion), Estimated Fair Value $ 16,015.4 $ 14,975.3
v3.26.1
Goodwill (Narrative) (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Goodwill [Line Items]    
Goodwill $ 1,485.9 $ 1,485.9
NIPSCO Operations    
Goodwill [Line Items]    
Goodwill 17.8  
Columbia Operations    
Goodwill [Line Items]    
Goodwill 1,468.1  
Corporate and Other    
Goodwill [Line Items]    
Goodwill $ 0.0  
v3.26.1
Goodwill (Schedule of Goodwill) (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Goodwill [Line Items]    
Goodwill $ 1,485.9 $ 1,485.9
Corporate and Other    
Goodwill [Line Items]    
Goodwill $ 0.0  
v3.26.1
Income Taxes (Narrative) (Details)
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Rate
Jun. 30, 2025
Rate
Jun. 30, 2026
Rate
Jun. 30, 2025
Rate
Income Tax Disclosure [Abstract]        
Effective income tax rates 21.70% 19.10% 13.90% 17.10%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate     21.00%  
Increase (Decrease) in Effective Tax Rate 2.60%   (3.20%)  
v3.26.1
Pension And Other Postretirement Benefits (Narrative) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Pension Plan        
Defined Benefit Plan Disclosure [Line Items]        
Employer contributions     $ 2.6 $ 1.0
Postemployment Benefits [Abstract]        
Defined Benefit Plan, Expected Return (Loss) on Plan Assets $ 22.5 $ 23.1 45.0 46.2
Other Postretirement Benefit Plan        
Defined Benefit Plan Disclosure [Line Items]        
Employer contributions     11.1 10.5
Postemployment Benefits [Abstract]        
Defined Benefit Plan, Expected Return (Loss) on Plan Assets $ 4.2 $ 4.2 $ 8.3 $ 8.4
v3.26.1
Pension And Other Postretirement Benefits (Components Of The Plans' Net Periodic Benefits Cost) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Pension Plan        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost $ 5.2 $ 4.9 $ 10.5 $ 9.8
Interest cost 14.1 16.0 28.2 32.0
Expected return on assets (22.5) (23.1) (45.0) (46.2)
Amortization of prior service credit 0.0 0.0 0.0 0.0
Recognized actuarial loss 5.9 6.4 11.8 12.8
Total Net Periodic Benefits Cost 2.7 4.2 5.5 8.4
Other Postretirement Benefit Plan        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost 0.9 1.0 1.7 2.0
Interest cost 4.6 5.6 9.2 11.2
Expected return on assets (4.2) (4.2) (8.3) (8.4)
Amortization of prior service credit (1.1) (0.4) (2.2) (0.8)
Recognized actuarial loss 0.0 0.4 0.1 0.8
Total Net Periodic Benefits Cost $ 0.2 $ 2.4 $ 0.5 $ 4.8
v3.26.1
Variable Interest Entities (Narrative) (Details)
$ in Millions
 3 Months Ended 6 Months Ended 12 Months Ended
Oct. 28, 2025
USD ($)
Rate
Jun. 30, 2026
USD ($)
Rate
MW
Jun. 30, 2025
USD ($)
Jun. 30, 2026
USD ($)
Rate
MW
Jun. 30, 2025
USD ($)
Dec. 31, 2025
USD ($)
Variable Interest Entity [Line Items]            
Wind Power Purchase Agreement, Purchase Percentage | Rate   100.00%   100.00%    
Income Taxes   $ 10.2 $ 23.8 $ 96.0 $ 129.5  
Contributions from NIPSCO and GenCo minority interest holders       124.5 134.3  
Payments to Noncontrolling Interests   27.1 26.9 47.0 44.4  
Business Combination, Price of Acquisition, Expected $ 35.2          
Current assets [1]   2,199.4   2,199.4   $ 2,377.2
Total Assets   37,543.6   37,543.6   35,858.7
Current liabilities [2]   4,414.5   4,414.5   3,457.4
Increase (Decrease) in Other Regulatory Assets       10.0   0.0
Variable Interest Entity Primary Beneficiary Member GenCo            
Variable Interest Entity [Line Items]            
Other Assets   210.7   210.7   305.4
us-gaap_VariableInterestEntityPrimaryBeneficiaryMemberGenCo            
Variable Interest Entity [Line Items]            
Contributions from NIPSCO and GenCo minority interest holders   39.8   47.8    
Payments to Noncontrolling Interests       0.0    
Current assets   174.3   174.3   62.5
Other Assets   213.9   213.9   305.4
Total Assets   928.3   928.3   407.6
Current liabilities   322.5   322.5   40.8
Total Liabilities   322.5   322.5   40.8
Property, Plant, and Equipment, after Accumulated Depreciation, Depletion, and Amortization   530.1   530.1   $ 39.7
NIPSCO Holdings II            
Variable Interest Entity [Line Items]            
Contributions from NIPSCO and GenCo minority interest holders   $ 51.2 $ 99.5 $ 76.7 $ 134.3  
NIPSCO Holdings II            
Variable Interest Entity [Line Items]            
Subsidiary, Ownership Percentage, Parent | Rate 19.90%          
Rosewater            
Variable Interest Entity [Line Items]            
Nameplate Capacity | MW   102   102    
Indiana Crossroads Wind            
Variable Interest Entity [Line Items]            
Nameplate Capacity | MW   302   302    
Indiana Crossroads Solar            
Variable Interest Entity [Line Items]            
Nameplate Capacity | MW   200   200    
Dunns Bridge I            
Variable Interest Entity [Line Items]            
Nameplate Capacity | MW   265   265    
[1] Includes $1,764.0 million and $1,312.7 million at June 30, 2026 and December 31, 2025, respectively, of net property, plant and equipment assets and $223.4 million and $90.1 million at June 30, 2026 and December 31, 2025, respectively, of current assets of consolidated VIEs that may be used only to settle obligations of the consolidated VIEs. Refer to Note 4, "Noncontrolling Interests," for additional information.
(2)Includes $210.7 million and $305.4 million at June 30, 2026 and December 31, 2025, respectively, of advanced deposits of project costs and $10.0 million and zero, respectively, of regulatory assets at June 30, 2026 and December 31, 2025, respectively, of consolidated VIEs that may be used only to settle obligations of the consolidated VIEs. Refer to Note 4, "Noncontrolling Interests," for additional information.
[2] Includes $335.6 million and $56.9 million at June 30, 2026 and December 31, 2025, respectively, of current liabilities and $57.0 million and $55.7 million at June 30, 2026 and December 31, 2025, respectively, of other liabilities, and finance leases of $40.0 million and $40.1 million at June 30, 2026 and December 31, 2025, respectively, of consolidated VIEs that creditors do not have recourse to our general credit. Refer to Note 4, "Noncontrolling Interests," for additional information.
v3.26.1
Variable Interest Entities (Schedule of VIE Assets and Liabilities) (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Variable Interest Entity [Line Items]    
Public Utilities, Property, Plant and Equipment, Net [1] $ 30,521.3 $ 28,688.2
Current assets [1] 2,199.4 2,377.2
Other Assets, Noncurrent 4,529.9 4,520.5
Total Assets 37,543.6 35,858.7
Current liabilities [2] 4,414.5 3,457.4
Asset retirement obligations 811.8 781.9
Finance lease obligations 381.5 258.0
Variable Interest Entity, Primary Beneficiary    
Variable Interest Entity [Line Items]    
Finance Lease, Liability, Payment, Due 40.0 40.1
Variable Interest Entity Primary Beneficiary Member GenCo    
Variable Interest Entity [Line Items]    
Other Assets 210.7 305.4
Consolidated Variable Interest Entities    
Variable Interest Entity [Line Items]    
Public Utilities, Property, Plant and Equipment, Net 1,233.9 1,273.0
Current assets 49.1 27.6
Total Assets 1,283.0 1,300.6
Current liabilities 13.1 16.1
Asset retirement obligations 57.0 55.7
Total Liabilities $ 110.1 $ 111.9
[1] Includes $1,764.0 million and $1,312.7 million at June 30, 2026 and December 31, 2025, respectively, of net property, plant and equipment assets and $223.4 million and $90.1 million at June 30, 2026 and December 31, 2025, respectively, of current assets of consolidated VIEs that may be used only to settle obligations of the consolidated VIEs. Refer to Note 4, "Noncontrolling Interests," for additional information.
(2)Includes $210.7 million and $305.4 million at June 30, 2026 and December 31, 2025, respectively, of advanced deposits of project costs and $10.0 million and zero, respectively, of regulatory assets at June 30, 2026 and December 31, 2025, respectively, of consolidated VIEs that may be used only to settle obligations of the consolidated VIEs. Refer to Note 4, "Noncontrolling Interests," for additional information.
[2] Includes $335.6 million and $56.9 million at June 30, 2026 and December 31, 2025, respectively, of current liabilities and $57.0 million and $55.7 million at June 30, 2026 and December 31, 2025, respectively, of other liabilities, and finance leases of $40.0 million and $40.1 million at June 30, 2026 and December 31, 2025, respectively, of consolidated VIEs that creditors do not have recourse to our general credit. Refer to Note 4, "Noncontrolling Interests," for additional information.
v3.26.1
Long-Term Debt (Narrative) (Details)
May 26, 2026
USD ($)
Jun. 30, 2026
USD ($)
MW
May 18, 2026
USD ($)
Standby Letters of Credit      
Debt Instrument [Line Items]      
Revolving credit facility interest rate of 2.13% at March 31, 2020   $ 119,000,000.0  
Rosewater      
Debt Instrument [Line Items]      
Nameplate Capacity | MW   102  
Senior Notes | NiSource      
Debt Instrument [Line Items]      
Senior Notes $ 500,000,000.0   $ 750,000,000.0
Debt, Weighted Average Interest Rate   4.75%  
Proceeds from Debt, Net of Issuance Costs $ 1,236,000,000    
Unsecured Debt | NiSource      
Debt Instrument [Line Items]      
Debt, Weighted Average Interest Rate   5.30%  
v3.26.1
Short-Term Borrowings (Narrative) (Details)
$ in Millions
 6 Months Ended
Jun. 30, 2026
USD ($)
Dec. 31, 2025
USD ($)
Short-term Debt [Line Items]    
Short-term debt due to asset securitization $ 0.0 $ 0.0
Short-term Debt $ 692.0 736.0
Accounts Receivable Program    
Short-term Debt [Line Items]    
Number of Agreements 3  
Cash From Financing Activities Related To The Change In Short-Term Borrowings Due To The Securitization Transactions $ 0.0  
Short-term Debt 245.0  
Revolving Credit Facility    
Short-term Debt [Line Items]    
Line of Credit Facility, Maximum Borrowing Capacity 2,500.0  
Long-term Line of Credit 0.0 0.0
Commercial Paper    
Short-term Debt [Line Items]    
Line of Credit Facility, Maximum Borrowing Capacity 2,500.0  
Commercial paper outstanding $ 692.0 $ 736.0
Short-term Debt, Weighted Average Interest Rate, at Point in Time 4.00% 3.92%
v3.26.1
Other Commitments And Contingencies (Narrative) (Details)
$ in Millions
 3 Months Ended 6 Months Ended
Oct. 28, 2025
USD ($)
Rate
Jun. 30, 2026
USD ($)
Rate
MW
Jun. 30, 2026
USD ($)
Rate
MW
Dec. 31, 2025
USD ($)
Other Commitments And Contingencies [Line Items]        
Guaranty Liabilities   $ 27.2 $ 27.2  
Recorded reserves to cover environmental remediation at various sites   $ 80.2 $ 80.2 $ 82.6
Wind Power Purchase Agreement, Purchase Percentage | Rate   100.00% 100.00%  
Business Combination, Price of Acquisition, Expected $ 35.2      
Contractual Obligation   $ 52.2 $ 52.2 52.0
Long-Term Purchase Commitment, Amount   658.7    
Noncancelable Commitments - e-storage   122.7 122.7  
Guarantor Obligations, Maximum Exposure, Undiscounted   $ 245.4 245.4  
2028 through 2030 market capacity purchase commitments     174.6  
Capacity Purchase Commitments     $ 1,100.0  
NIPSCO Holdings II        
Other Commitments And Contingencies [Line Items]        
Subsidiary, Ownership Percentage, Parent | Rate 19.90%      
MGP Sites        
Other Commitments And Contingencies [Line Items]        
Number of waste disposal sites identified by program   36 36  
Liability for Estimated Remediation Costs   $ 72.6 $ 72.6 $ 75.5
us-gaap_VariableInterestEntityPrimaryBeneficiaryMemberGenCo        
Other Commitments And Contingencies [Line Items]        
Nameplate Capacity | MW   167 167  
Standby Letters of Credit        
Other Commitments And Contingencies [Line Items]        
Long-term Line of Credit   $ 119.0 $ 119.0  
v3.26.1
Accumulated Other Comprehensive Loss (Components Of Accumulated Other Comprehensive Loss) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance $ 11,927.5 $ 10,946.0 $ 11,659.9 $ 10,668.3
Other Comprehensive Income (Loss) before reclassifications (0.5) 0.9 (3.5) 2.0
Amounts reclassified from accumulated other comprehensive income (loss) 0.2 0.1 0.2 0.2
Net current-period other comprehensive income (loss) (0.3) 1.0 (3.3) 2.2
Ending balance 11,894.4 10,996.9 11,894.4 10,996.9
Interest Rate Risk        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Net current-period other comprehensive income (loss)     (0.2)  
Accumulated Other Comprehensive Income (Loss)        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (9.2) (29.2) (6.2) (30.4)
Net current-period other comprehensive income (loss) (0.3)   (3.3)  
Ending balance (9.5) (28.2) (9.5) (28.2)
Gains and Losses on Securities        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (1.1) (3.2) 0.1 (4.0)
Other Comprehensive Income (Loss) before reclassifications 0.6 1.0 (0.6) 1.8
Amounts reclassified from accumulated other comprehensive income (loss) 0.1 0.0 0.1 0.0
Net current-period other comprehensive income (loss) 0.7 1.0 (0.5) 1.8
Ending balance (0.4) (2.2) (0.4) (2.2)
Gains and Losses on Cash Flow Hedges        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (13.7) (13.3) (13.6) (13.2)
Other Comprehensive Income (Loss) before reclassifications 0.0 0.0 0.0 0.0
Amounts reclassified from accumulated other comprehensive income (loss) (0.1) (0.1) (0.2) (0.2)
Net current-period other comprehensive income (loss) (0.1) (0.1)   (0.2)
Ending balance (13.8) (13.4) (13.8) (13.4)
Pension and OPEB Items        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance 5.6 (12.7) 7.3 (13.2)
Other Comprehensive Income (Loss) before reclassifications (1.1) (0.1) (2.9) 0.2
Amounts reclassified from accumulated other comprehensive income (loss) 0.2 0.2 0.3 0.4
Net current-period other comprehensive income (loss) (0.9) 0.1 (2.6) 0.6
Ending balance $ 4.7 $ (12.6) $ 4.7 $ (12.6)
v3.26.1
Other, Net (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Other, Net [Abstract]        
Accounts receivable $ 1.6 $ 1.5 $ 6.3 $ 3.5
Gas storage and other inventories 14.6 8.6 24.4 17.8
Customer deposits and credits 2.2 (1.6) 4.4 (5.4)
Income Tax Examination, Penalties Expense 0.0 (8.1) 0.0 (9.2)
Other, net 18.2 0.5 32.6 6.3
Miscellaneous Non-Operating Income (Expense) $ (0.2) $ 0.1 $ (2.5) $ (0.4)
v3.26.1
Business Segment Information (Narrative) (Details)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
USD ($)
Jun. 30, 2025
USD ($)
Jun. 30, 2026
USD ($)
segment
Jun. 30, 2025
USD ($)
Segment Reporting [Abstract]        
Primary business segments | segment     2  
Segment Reporting [Line Items]        
Primary business segments | segment     2  
Regulated Operating Revenue $ 1,342.4 $ 1,283.0 $ 3,705.5 $ 3,466.2
Operating Income (Loss) 228.1 262.9 1,047.3 1,022.3
Corporate and Other        
Segment Reporting [Line Items]        
Regulated Operating Revenue 163.4 144.6 310.7 290.0
Operating Income (Loss) 4.4 6.7 2.8 8.4
Eliminations        
Segment Reporting [Line Items]        
Regulated Operating Revenue $ (165.7) $ (147.1) $ (315.3) $ (294.8)
v3.26.1
Business Segment Information (Schedule Of Operating Income Derived From Revenues And Expenses By Segment) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Segment Reporting [Line Items]          
Consolidated Operating Income (Loss) $ 228.1 $ 262.9 $ 1,047.3 $ 1,022.3  
Total Assets 37,543.6   37,543.6   $ 35,858.7
Regulated Operating Revenue 1,342.4 1,283.0 3,705.5 3,466.2  
Cost of energy 193.6 261.8 862.8 909.3  
Utilities Operating Expense, Maintenance and Operations 474.9 396.2 964.1 824.0  
Taxes, Miscellaneous 83.6 74.2 180.8 163.8  
Depreciation, Depletion and Amortization 362.2 286.7 650.5 545.3  
Operating Segments          
Segment Reporting [Line Items]          
Consolidated Operating Income (Loss) 223.7 256.2 1,044.5 1,013.9  
Regulated Operating Revenue 1,344.7 1,285.5 3,710.1 3,471.0  
Cost of energy 192.6 261.8 861.8 909.3  
Utilities Operating Expense, Maintenance and Operations 495.6 418.7 995.4 863.7  
Taxes, Miscellaneous 79.2 70.5 171.2 156.0  
Segment Reporting, Other Segment Item, Amount   0.7   1.0  
Depreciation, Depletion and Amortization 353.6 277.6 637.2 527.1  
Operating Segments | Nonrelated Party          
Segment Reporting [Line Items]          
Regulated Operating Revenue 1,340.9 1,281.8 3,702.6 3,463.8  
Operating Segments | Related Party          
Segment Reporting [Line Items]          
Regulated Operating Revenue 3.8 3.7 7.5 7.2  
Corporate and Other          
Segment Reporting [Line Items]          
Consolidated Operating Income (Loss) 4.4 6.7 2.8 8.4  
Total Assets 2,218.7   2,218.7   1,828.3
Regulated Operating Revenue 163.4 144.6 310.7 290.0  
Eliminations          
Segment Reporting [Line Items]          
Regulated Operating Revenue (165.7) (147.1) (315.3) (294.8)  
Corporate and Other | Unaffiliated          
Segment Reporting [Line Items]          
Revenues 1.5 1.2 2.9 2.4  
Columbia Operations | Unaffiliated          
Segment Reporting [Line Items]          
Revenues     1,920.2 1,841.8  
Columbia Operations | Intersegment          
Segment Reporting [Line Items]          
Revenues       6.7  
Columbia Operations | Operating Segments          
Segment Reporting [Line Items]          
Consolidated Operating Income (Loss) 103.3 122.2 575.6 568.0  
Total Assets 16,258.5   16,258.5   15,903.7
Regulated Operating Revenue 600.5 604.7 1,927.1 1,848.5  
Cost of energy 80.8 110.4 464.7 490.2  
Utilities Operating Expense, Maintenance and Operations 225.2 207.7 503.6 450.7  
Taxes, Miscellaneous 59.8 52.4 130.9 119.4  
Segment Reporting, Other Segment Item, Amount   0.3   0.3  
Depreciation, Depletion and Amortization 131.4 111.7 252.3 219.9  
Columbia Operations | Operating Segments | Nonrelated Party          
Segment Reporting [Line Items]          
Regulated Operating Revenue 597.0 601.2 1,920.2    
Columbia Operations | Operating Segments | Related Party          
Segment Reporting [Line Items]          
Regulated Operating Revenue 3.5 3.5 6.9    
NIPSCO Operations          
Segment Reporting [Line Items]          
Regulated Operating Revenue 743.9 680.6      
NIPSCO Operations | Unaffiliated          
Segment Reporting [Line Items]          
Revenues       1,622.0  
NIPSCO Operations | Intersegment          
Segment Reporting [Line Items]          
Revenues       0.5  
NIPSCO Operations | Operating Segments          
Segment Reporting [Line Items]          
Consolidated Operating Income (Loss) 120.4 134.0 468.9 445.9  
Total Assets 19,066.4   19,066.4   $ 18,126.7
Regulated Operating Revenue 744.2 680.8 1,783.0 1,622.5  
Cost of energy 111.8 151.4 397.1 419.1  
Utilities Operating Expense, Maintenance and Operations 270.4 211.0 491.8 413.0  
Taxes, Miscellaneous 19.4 18.1 40.3 36.6  
Segment Reporting, Other Segment Item, Amount   0.4   0.7  
Depreciation, Depletion and Amortization 222.2 165.9 384.9 $ 307.2  
NIPSCO Operations | Operating Segments | Nonrelated Party          
Segment Reporting [Line Items]          
Regulated Operating Revenue 743.9 680.6 1,782.4    
NIPSCO Operations | Operating Segments | Related Party          
Segment Reporting [Line Items]          
Regulated Operating Revenue $ 0.3 $ 0.2 $ 0.6    
v3.26.1
Supplemental Disclosures of Cash Flow Information (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Supplemental Cash Flow Elements [Abstract]        
Accounts Receivable, Sale $ 343.5 $ 185.6    
Increase (Decrease) in Income Taxes Receivable     $ 11.8 $ 0.0
Increase (Decrease) in Finished Goods and Work in Process Inventories 60.6 20.9    
Increase (Decrease) in Accounts Payable (238.9) (146.9)    
Customer Advances and Deposits (119.5) (108.9)    
Increase (Decrease) in Accrued Taxes Payable 21.0 (0.7)    
Debt Instrument, Increase, Accrued Interest 35.0 20.5    
Increase Decrease In Exchange Gas Receivable Payable   73.8 (215.6)  
Increase Decrease In Other Accruals (20.8) (17.6)    
Increase Decrease In Prepayments And Other Current Assets (116.5) (28.4)    
Employee Benefits and Share-Based Compensation (32.6) (63.1)    
Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital (272.0) (64.8)    
Dividends Payable, Current $ 148.0 $ 135.1 148.0 135.1
Capital expenditures included in current liabilities     678.8 426.6
Advance deposits transferred to capital expenditures     $ 108.6 $ 0.0
v3.26.1
Subsequent Event (Narrative) (Details) - USD ($)
$ in Millions
 6 Months Ended
Oct. 28, 2025
Jun. 30, 2026
Jun. 30, 2025
Subsequent Event [Line Items]      
Payment to renewable generation asset developer   $ 0.0 $ 958.0
Business Combination, Price of Acquisition, Expected $ 35.2    
NIPSCO Holdings II      
Subsequent Event [Line Items]      
Subsidiary, Ownership Percentage, Parent 19.90%