NISOURCE INC., 10-Q filed on 10/29/2025
Quarterly Report
v3.25.3
Document And Entity Information - shares
 9 Months Ended
Sep. 30, 2025
Oct. 22, 2025
Document Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Sep. 30, 2025  
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 (877)  
Local Phone Number 647-5990  
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   477,195,529
Entity Central Index Key 0001111711  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q3  
Amendment Flag false  
Common Stock    
Document Information [Line Items]    
Title of 12(b) Security Common Stock, par value $0.01 per share  
Trading Symbol NI  
Security Exchange Name NYSE  
v3.25.3
Statements of Consolidated Income (Loss) - USD ($)
shares in Millions, $ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Operating Revenues        
Customer revenues $ 1,240.2 $ 1,046.1 $ 4,636.2 $ 3,743.2
Other revenues 32.9 30.2 103.1 124.1
Total Operating Revenues 1,273.1 1,076.3 4,739.3 3,867.3
Loss on sale of assets (0.6) (0.5) 0.2 1.1
Operating Expenses        
Cost of energy 193.6 165.9 1,102.9 755.6
Operation and maintenance 401.1 357.4 1,225.1 1,093.5
Depreciation and amortization 306.9 269.5 852.2 765.1
Loss on impairment of assets 0.0 0.0 0.7 2.9
Other taxes 74.6 65.7 238.4 210.4
Operating Costs and Expenses 975.6 858.0 3,419.5 2,828.6
Operating Income 297.5 218.3 1,319.8 1,038.7
Other Income (Deductions)        
Interest expense, net (179.8) (134.6) (451.7) (380.2)
Other, net 9.9 29.2 16.2 51.4
Total Other Deductions, Net (169.9) (105.4) (435.5) (328.8)
Income before Income Taxes 127.6 112.9 884.3 709.9
Income Taxes 20.6 15.9 150.1 109.5
Net Income 107.0 97.0 734.2 600.4
Net income attributable to noncontrolling interest 12.3 11.3 62.5 63.9
Net Income Attributable to NiSource 94.7 85.7 671.7 536.5
Preferred Stock Redemption Premium 0.0 0.0 0.0 (14.0)
Preferred dividends 0.0 0.0 0.0 (6.7)
Net Income Available to Common Shareholders $ 94.7 $ 85.7 $ 671.7 $ 515.8
Earnings Per Share        
Basic Earnings Per Share $ 0.20 $ 0.19 $ 1.42 $ 1.15
Diluted Earnings Per Share $ 0.20 $ 0.19 $ 1.42 $ 1.14
Basic Average Common Shares Outstanding 472.1 451.9 471.1 449.4
Diluted Average Common Shares 473.7 454.5 472.8 451.4
Noncontrolling Interest        
Other Income (Deductions)        
Net income attributable to noncontrolling interest $ 12.3 $ 11.3 $ 62.5 $ 63.9
v3.25.3
Statements of Consolidated Comprehensive Income (Loss) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Net Income $ 107.0 $ 97.0 $ 734.2 $ 600.4
Other comprehensive income:        
Net unrealized loss on available-for-sale securities [1] 1.3 3.5 3.1 3.2
Net unrealized gain (loss) on cash flow hedges (0.1) (0.1) (0.3) (0.3)
Unrecognized pension and OPEB benefit (costs) [2] 14.0 0.6 14.6 1.1
Total other comprehensive income 15.2 4.0 17.4 4.0
Comprehensive Income $ 122.2 $ 101.0 $ 751.6 $ 604.4
[1] Net unrealized gain on available-for-sale debt securities, net of $0.3 million tax expense and $0.9 million tax expense in the third quarter of 2025 and 2024, respectively, and $0.8 million tax expense for the nine months ended 2025 and 2024, respectively.
(2)Reclassification adjustment for cash flow hedges, net of $0.1 million tax benefit and $0.1 million tax benefit in the third quarter of 2025 and 2024, respectively, and $0.2 million tax benefit and $0.1 million tax benefit for the nine months ended 2025 and 2024, respectively.
[2] Unrecognized pension and OPEB benefit, net of $4.6 million tax expense and $0.2 million tax expense in the third quarter of 2025 and 2024, respectively, and $4.8 million tax expense and $0.4 million tax expense for the nine months ended 2025 and 2024, respectively.
v3.25.3
Statements of Consolidated Comprehensive Income (Loss) (Parenthetical) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax $ (0.3) $ (0.9) $ (0.8)  
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax 0.1 0.1 0.2 $ 0.1
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax $ (4.6) $ (0.2) $ (4.8) $ (0.4)
v3.25.3
Statements of Consolidated Balance Sheets - USD ($)
$ in Millions
Sep. 30, 2025
Dec. 31, 2024
Property, Plant and Equipment    
Plant $ 37,201.7 $ 34,152.9
Accumulated depreciation and amortization (9,201.6) (8,699.0)
Net Property, Plant and Equipment [1] 28,000.1 25,453.9
Investments and Other Assets    
Unconsolidated affiliates 7.7 6.5
Available-for-sale debt securities (amortized cost of $160.4 and $91.9, allowance for credit losses of $0.1 and $0.1, respectively) 159.0 86.7
Other investments 116.2 85.5
Total Investments and Other Assets 282.9 178.7
Current Assets    
Cash and cash equivalents 95.0 156.6
Restricted Cash 24.5 42.0
Accounts receivable 719.6 987.9
Allowance for credit losses (18.6) (23.7)
Accounts receivable, net 701.0 964.2
Gas storage 268.3 179.6
Materials and supplies, at average cost 183.3 173.3
Electric production fuel, at average cost 23.7 36.2
Exchange gas receivable 42.9 45.7
Regulatory assets 326.5 319.9
Prepayments and other 25.6 24.2
Total Current Assets [1] 1,848.2 2,080.2
Other Assets    
Regulatory assets 2,132.9 2,157.4
Goodwill 1,485.9 1,485.9
Deferred charges and other 652.9 432.0
Total Other Assets 4,271.7 4,075.3
Total Assets 34,402.9 31,788.1
Stockholders' Equity    
Common stock - $0.01 par value,750,000,000 shares authorized; 477,136,079 and 469,822,472 shares outstanding, respectively 4.8 4.7
Treasury stock (99.9) (99.9)
Additional paid-in capital 9,798.3 9,521.5
Retained deficit (572.0) (711.7)
Accumulated other comprehensive loss (13.0) (30.4)
Total NiSource Stockholders’ Equity 9,118.2 8,684.2
Noncontrolling interest in consolidated subsidiaries 2,123.6 1,984.1
Total Stockholders’ Equity 11,241.8 10,668.3
Long-term debt, excluding amounts due within one year 14,472.1 12,074.5
Total Capitalization 25,713.9 22,742.8
Current Liabilities    
Current portion of long-term debt 31.3 1,281.2
Short-term borrowings 1,260.0 604.6
Accounts payable 712.0 863.1
Dividends payable - common stock 137.4 0.0
Customer deposits and credits 273.5 268.8
Taxes accrued 179.0 173.4
Interest accrued 198.2 157.0
Exchange gas payable 100.0 91.8
Regulatory liabilities 192.0 150.5
Asset Retirement Obligation 66.3 84.6
Accrued compensation and employee benefits 218.0 268.2
Other accruals 165.7 170.2
Total Current Liabilities [2] 3,533.4 4,113.4
Other Liabilities    
Deferred income taxes 2,405.4 2,281.6
Accrued liability for postretirement and postemployment benefits 174.4 207.5
Regulatory liabilities 1,487.0 1,431.2
Asset retirement obligations 751.4 698.6
Other noncurrent liabilities 337.4 313.0
Total Other Liabilities [2] 5,155.6 4,931.9
Total Capitalization and Liabilities $ 34,402.9 $ 31,788.1
Common Stock, Shares Authorized 750,000,000 750,000,000
Common Stock, No Par Value $ 0.01 $ 0.01
Prepaid Expense, Current $ 157.4 $ 138.5
Joint Ventures    
Property, Plant and Equipment    
Net Property, Plant and Equipment 1,284.4  
Current Assets    
Total Current Assets 59.6 65.0
Current Liabilities    
Total Current Liabilities 54.4 53.7
Other Liabilities    
Total Other Liabilities $ 55.0 $ 58.3
[1] Includes $1,284.4 million and $1,323.8 million at September 30, 2025 and December 31, 2024, respectively, of net property, plant and equipment assets and $59.6 million and $65.0 million at September 30, 2025 and December 31, 2024, 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 $54.4 million and $53.7 million at September 30, 2025 and December 31, 2024, respectively, of current liabilities and $55.0 million and $58.3 million at September 30, 2025 and December 31, 2024, respectively, of other liabilities, and finance leases of $40.2 million and $40.4 million at September 30, 2025 and December 31, 2024 respectively, of consolidated VIEs that creditors do not have recourse to our general credit. Refer to Note 4, "Noncontrolling Interests," for additional information.
v3.25.3
Statements of Consolidated Balance Sheets (Parenthetical) - USD ($)
$ in Millions
Sep. 30, 2025
Dec. 31, 2024
Amortized Cost $ 160.4 $ 91.9
Allowance for Credit Loss $ 0.1 $ 0.1
Common Stock, Shares Authorized 750,000,000 750,000,000
Common Stock, Shares, Outstanding 477,136,079 469,822,472
Public Utilities, Property, Plant and Equipment, Net [1] $ 28,000.1 $ 25,453.9
Current assets [1] 1,848.2 2,080.2
Current liabilities [2] 3,533.4 4,113.4
Other Liabilities [2] 5,155.6 4,931.9
Joint Ventures    
Public Utilities, Property, Plant and Equipment, Net 1,284.4  
Current assets 59.6 65.0
Current liabilities 54.4 53.7
Other Liabilities $ 55.0 $ 58.3
[1] Includes $1,284.4 million and $1,323.8 million at September 30, 2025 and December 31, 2024, respectively, of net property, plant and equipment assets and $59.6 million and $65.0 million at September 30, 2025 and December 31, 2024, 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 $54.4 million and $53.7 million at September 30, 2025 and December 31, 2024, respectively, of current liabilities and $55.0 million and $58.3 million at September 30, 2025 and December 31, 2024, respectively, of other liabilities, and finance leases of $40.2 million and $40.4 million at September 30, 2025 and December 31, 2024 respectively, of consolidated VIEs that creditors do not have recourse to our general credit. Refer to Note 4, "Noncontrolling Interests," for additional information.
v3.25.3
Statements of Consolidated Cash Flows - USD ($)
$ in Millions
 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Operating Activities    
Net Income $ 734.2 $ 600.4
Adjustments to Reconcile Net Income to Net Cash from Operating Activities:    
Depreciation and amortization 852.2 765.1
Deferred income taxes and investment tax credits 153.5 109.1
Loss on sale of assets 0.2 1.1
Payments for asset retirement obligations (50.0) (55.0)
Other adjustments 22.5 (14.9)
Changes in Assets and Liabilities:    
Components of working capital(1) (26.0) (85.8)
Regulatory assets/liabilities (19.5) (35.6)
Deferred charges and other noncurrent assets (24.4) (45.1)
Other noncurrent liabilities and deferred credits 7.0 2.4
Net Cash Flows from Operating Activities 1,649.7 1,241.7
Investing Activities    
Capital expenditures (1,936.0) (1,854.0)
Payment to renewable generation asset developer (1,091.7) (478.8)
Advanced deposits (161.3) 0.0
Other investing activities (93.8) 27.2
Net Cash Flows used for Investing Activities (3,396.6) (2,414.5)
Financing Activities    
Proceeds from issuance of long-term debt 2,362.0 2,229.6
Repayments of finance lease obligations (17.3) (20.4)
Repayments of Long-Term Debt (1,250.0) 0.0
Repayment of short-term debt (maturity > 90 days) 0.0 (1,650.0)
Net change in commercial paper and other short-term borrowings 655.4 (1,141.6)
Issuance of common stock, net of issuance costs 259.1 507.9
Redemption of preferred stock 0.0 (486.1)
Preferred stock redemption premium 0.0 (14.0)
Equity costs, premiums and other debt related costs (22.0) (62.9)
Contributions from NIPSCO minority interest holders 145.3 99.5
Distributions to tax equity partners (12.8) (14.3)
Distribution to NIPSCO minority interest holders (55.5) (32.0)
Dividends paid - common stock (396.4) (357.0)
Dividends paid - preferred stock 0.0 (8.2)
Net Cash Flows from (used for) Financing Activities 1,667.8 (949.5)
Change in cash, cash equivalents and restricted cash (79.1) (2,122.3)
Cash, cash equivalents and restricted cash at beginning of period 198.6 2,281.1
Cash, Cash Equivalents and Restricted Cash at End of Period 119.5 158.8
Cost of removal (113.8) (108.9)
NIPSCO minority interest holders    
Financing Activities    
Contributions from NIPSCO minority interest holders $ 145.3 $ 99.5
v3.25.3
Statement of Consolidated Cash Flows (Schedule of Balance Sheet Reconciliation) - USD ($)
$ in Millions
Sep. 30, 2025
Dec. 31, 2024
Sep. 30, 2024
Dec. 31, 2023
Cash and Cash Equivalent $ 95.0 $ 156.6    
Restricted Cash 24.5 42.0    
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents $ 119.5 $ 198.6 $ 158.8 $ 2,281.1
v3.25.3
Statements of Consolidated Cash Flows (Supplemental Disclosures of Cash Flow Information) - USD ($)
$ in Millions
 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]    
Capital expenditures included in current liabilities $ 408.2 $ 348.0
v3.25.3
Statements of Consolidated Equity - USD ($)
$ in Millions
Total
Common Stock
Preferred Stock
Treasury Stock, Common
Additional Paid-in Capital
Retained Deficit
Accumulated Other Comprehensive Income (Loss)
Noncontrolling Interest
Forward March 03
Beginning balance at Dec. 31, 2023 $ 10,136.3 $ 4.5 $ 486.1 $ (99.9) $ 8,879.5 $ (967.0) $ (33.6) $ 1,866.7  
Comprehensive Income:                  
Net Income 600.4         536.5      
Net current-period other comprehensive income (loss) 4.0                
Other comprehensive income (loss), net of tax   0.0 0.0 0.0 0.0 0.0 4.0 0.0  
Dividends:                  
Common stock (482.3)         (482.3)      
Preferred stock (8.1)         (8.1)      
Contributions from noncontrolling interests (99.5)             (99.5)  
Distributions to noncontrolling interests (46.3)     0.0       (46.3)  
Stock Issuances:                  
Equity Units (486.1)   (486.1)            
Employee stock purchase plan 4.7       4.7        
Long-term incentive plan 14.9       (14.9)        
401(k) and profit sharing 7.0       7.0        
ATM program 498.8 (0.2)     498.6        
Ending balance at Sep. 30, 2024 10,328.8 4.7 0.0 (99.9) 9,404.7 (934.9) (29.6) 1,983.8  
Stock Issuances:                  
Series B and B-1 Preferred stock redemption premium (14.0)         (14.0)      
Net income attributable to noncontrolling interest 63.9             63.9  
Beginning balance at Jun. 30, 2024 9,819.6 4.5 0.0 (99.9) 8,894.2 (896.2) (33.6) 1,950.6  
Comprehensive Income:                  
Net Income 97.0         85.7      
Net current-period other comprehensive income (loss) 4.0                
Other comprehensive income (loss), net of tax 4.0           4.0    
Dividends:                  
Common stock (124.4)         (124.4)      
Contributions from noncontrolling interests (39.8)             (39.8)  
Distributions to noncontrolling interests (17.9)             (17.9)  
Stock Issuances:                  
Employee stock purchase plan 1.7       1.7        
Long-term incentive plan 8.0                
401(k) and profit sharing 2.2       2.2        
ATM program 498.8 (0.2)     498.6        
Ending balance at Sep. 30, 2024 10,328.8 4.7 0.0 (99.9) 9,404.7 (934.9) (29.6) 1,983.8  
Stock Issuances:                  
Net income attributable to noncontrolling interest 11.3             11.3  
Long-term incentive plan         8.0        
Beginning balance at Dec. 31, 2024 10,668.3 4.7 0.0 (99.9) 9,521.5 (711.7) (30.4) 1,984.1  
Comprehensive Income:                  
Net Income 734.2         671.7      
Net current-period other comprehensive income (loss) 17.4           17.4    
Other comprehensive income (loss), net of tax 17.4                
Dividends:                  
Common stock (532.0)         (532.0)      
Contributions from noncontrolling interests (145.3)             (145.3)  
Distributions to noncontrolling interests (68.3)             (68.3)  
Stock Issuances:                  
Employee stock purchase plan 5.5       5.5        
Long-term incentive plan 15.3       15.3        
401(k) and profit sharing 7.2       7.2        
ATM program 248.9 (0.1)     248.8        
Ending balance at Sep. 30, 2025 11,241.8 4.8 0.0 (99.9) 9,798.3 (572.0) (13.0) 2,123.6  
Stock Issuances:                  
Net income attributable to noncontrolling interest 62.5             62.5  
Beginning balance at Jun. 30, 2025 10,996.9 4.7 0.0 (99.9) 9,538.0 (532.1) (28.2) 2,114.4  
Comprehensive Income:                  
Net Income 107.0         94.7      
Net current-period other comprehensive income (loss) 15.2           15.2    
Other comprehensive income (loss), net of tax 15.2                
Dividends:                  
Common stock (134.6)         (134.6)      
Contributions from noncontrolling interests (11.0)             (11.0)  
Distributions to noncontrolling interests (14.1)             (14.1)  
Stock Issuances:                  
Employee stock purchase plan 1.9       1.9        
Long-term incentive plan 7.2       7.2        
401(k) and profit sharing 2.4       2.4        
ATM program 248.9 (0.1)     248.8        
Ending balance at Sep. 30, 2025 11,241.8 $ 4.8 $ 0.0 $ (99.9) $ 9,798.3 $ (572.0) $ (13.0) 2,123.6  
Stock Issuances:                  
Net income attributable to noncontrolling interest $ 12.3             $ 12.3  
Common Stock Aggregate Sale Price                 $ 69.9
v3.25.3
Statements of Consolidated Equity (Shares) - shares
Total
Preferred Stock
Common Stock
Treasury Stock, Common
Issued:        
Shares, Issued (447,382,000)      
Beginning balance at Dec. 31, 2023   40,000    
Beginning balance at Dec. 31, 2023     451,345,000  
Beginning balance at Dec. 31, 2023       3,963,000
Issued:        
Equity Units 0   0  
Employee stock purchase plan 170,000 0 170,000 0
Long-term incentive plan 761,000 0 761,000 0
401(k) and profit sharing 246,000 0 246,000 0
Preferred Stock Shares Redeemed (18,148,000)   (18,148,000) 0
Stock Redeemed or Called During Period, Shares   (40,000)    
Ending balance at Sep. 30, 2024   0    
Ending balance at Sep. 30, 2024 477,136,000      
Beginning balance at Dec. 31, 2023     451,345,000  
Beginning balance at Dec. 31, 2023       3,963,000
Ending balance at Sep. 30, 2024     481,099,000  
Ending balance at Sep. 30, 2024       3,963,000
Issued:        
Shares, Issued (448,399,000) 0 (452,362,000)  
Beginning balance at Jun. 30, 2024       3,963,000
Issued:        
Employee stock purchase plan 59,000 0 59,000 0
Long-term incentive plan 32,000 0 32,000 0
401(k) and profit sharing 69,000 0 69,000 0
Preferred Stock Shares Redeemed (18,148,000)   (18,148,000) 0
Ending balance at Sep. 30, 2024   0    
Ending balance at Sep. 30, 2024 477,136,000      
Beginning balance at Jun. 30, 2024       3,963,000
Ending balance at Sep. 30, 2024     481,099,000  
Ending balance at Sep. 30, 2024       3,963,000
Issued:        
Shares, Issued (466,707,000) 0 (470,670,000)  
Beginning balance at Dec. 31, 2024   0    
Beginning balance at Dec. 31, 2024 469,822,472      
Beginning balance at Dec. 31, 2024     473,785,000  
Beginning balance at Dec. 31, 2024       3,963,000
Issued:        
Employee stock purchase plan 141,000 0 141,000 0
Long-term incentive plan 768,000 0 768,000 0
401(k) and profit sharing 179,000 0 179,000 0
Preferred Stock Shares Redeemed (6,226,000)   (6,226,000) 0
Ending balance at Sep. 30, 2025   0    
Ending balance at Sep. 30, 2025 477,136,079      
Beginning balance at Dec. 31, 2024     473,785,000  
Beginning balance at Dec. 31, 2024       3,963,000
Ending balance at Sep. 30, 2025     481,099,000  
Ending balance at Sep. 30, 2025       3,963,000
Beginning balance at Jun. 30, 2025   0    
Beginning balance at Jun. 30, 2025 470,784,000      
Beginning balance at Jun. 30, 2025     474,747,000  
Beginning balance at Jun. 30, 2025       3,963,000
Issued:        
Employee stock purchase plan 47,000 0 47,000 0
Long-term incentive plan 24,000 0 24,000 0
401(k) and profit sharing 55,000 0 55,000 0
Preferred Stock Shares Redeemed (6,226,000)   (6,226,000) 0
Ending balance at Sep. 30, 2025   0    
Ending balance at Sep. 30, 2025 477,136,079      
Beginning balance at Jun. 30, 2025     474,747,000  
Beginning balance at Jun. 30, 2025       3,963,000
Ending balance at Sep. 30, 2025     481,099,000  
Ending balance at Sep. 30, 2025       3,963,000
v3.25.3
Statements Of Consolidated Equity (Parenthetical) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Common Stock, Dividends, Per Share, Declared $ 0.280 $ 0.265 $ 1.120 $ 1.060
Preferred Stock Redemption Premium $ 0.0 $ 0.0 $ 0.0 $ (14.0)
Distributions to noncontrolling interests 11.0 39.8 145.3 99.5
Preferred stock       (8.1)
Distributions to noncontrolling interests (14.1) (17.9) (68.3) (46.3)
Equity Units       (486.1)
Noncontrolling Interest        
Distributions to noncontrolling interests 11.0 39.8 145.3 99.5
Distributions to noncontrolling interests $ (14.1) $ (17.9) $ (68.3) (46.3)
Preferred Stock        
Equity Units       (486.1)
Treasury Stock, Common        
Distributions to noncontrolling interests       0.0
Retained Deficit        
Preferred stock       $ (8.1)
Series B Preferred Stock [Member]        
Preferred Stock, Dividends Per Share, Declared     $ 0 $ 406.25
v3.25.3
Basis of Accounting Presentation
 9 Months Ended
Sep. 30, 2025
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, 2024. 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.
v3.25.3
Recent Accounting Pronouncements
 9 Months Ended
Sep. 30, 2025
Accounting Standards Update and Change in Accounting Principle [Abstract]  
Recent Accounting Pronouncements
v3.25.3
Revenue Recognition
 9 Months Ended
Sep. 30, 2025
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 September 30, 2025
(in millions)
Columbia OperationsNIPSCO OperationsCorporate and OtherTotal
Gas Distribution
Residential$328.1 $72.9 $— $401.0 
Commercial95.1 32.2 — 127.3 
Industrial36.0 19.7 — 55.7 
Off-system13.8 — — 13.8 
Miscellaneous(1)
6.7 2.6 — 9.3 
Subtotal$479.7 $127.4 $— $607.1 
Electric Generation and Power Delivery
Residential$— $254.6 $— $254.6 
Commercial— 210.6 — 210.6 
Industrial— 156.2 — 156.2 
Wholesale— 18.4 — 18.4 
Miscellaneous(1)
— (6.7)— (6.7)
Subtotal $— $633.1 $— $633.1 
Total Customer Revenues(2)
479.7 760.5 — 1,240.2 
Other Revenues(3)
5.2 26.5 1.2 32.9 
Total Operating Revenues$484.9 $787.0 $1.2 $1,273.1 
(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 16, "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 non-jurisdictional transmission assets. Amounts included in Corporate and Other primarily relate to products and services revenue.
Three months ended September 30, 2024
(in millions)
Columbia Operations
NIPSCO Operations
Corporate and OtherTotal
Gas Distribution
Residential$296.9 $66.8 $— $363.7 
Commercial78.3 28.6 — 106.9 
Industrial32.0 16.4 — 48.4 
Off-system7.1 — — 7.1 
Wholesale0.1 — — 0.1 
Miscellaneous(1)
2.9 1.9 — 4.8 
Subtotal$417.3 $113.7 $— $531.0 
Electric Generation and Power Delivery
Residential$— $197.9 $— $197.9 
Commercial— 172.7 — 172.7 
Industrial— 124.8 — 124.8 
Wholesale— 15.0 — 15.0 
Public Authority— 2.0 — 2.0 
Miscellaneous(1)
— 2.7 — 2.7 
Subtotal$— $515.1 $— $515.1 
Total Customer Revenues(2)
417.3 628.8 — 1,046.1 
Other Revenues(3)
6.1 23.8 0.3 30.2 
Total Operating Revenues$423.4 $652.6 $0.3 $1,076.3 
(1)Amounts included in Columbia Operations 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 16, "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 non-jurisdictional transmission assets.
Nine months ended September 30, 2025
(in millions)
Columbia OperationsNIPSCO OperationsCorporate and OtherTotal
Gas Distribution
Residential$1,576.3 $478.5 $— $2,054.8 
Commercial527.8 180.8 — $708.6 
Industrial121.5 73.7 — $195.2 
Off-system58.9 — — $58.9 
Miscellaneous(1)
27.4 10.6 — $38.0 
Subtotal$2,311.9 $743.6 $— $3,055.5 
Electric Generation and Power Delivery
Residential$— $586.4 $— $586.4 
Commercial— 531.7 — $531.7 
Industrial— 432.3 — $432.3 
Wholesale— 37.9 — $37.9 
Miscellaneous(1)
— (7.6)— $(7.6)
Subtotal$— $1,580.7 $— $1,580.7 
Total Customer Revenues(2)
2,311.9 2,324.3 — 4,636.2 
Other Revenues(3)
14.8 84.7 3.6 103.1 
Total Operating Revenues$2,326.7 $2,409.0 $3.6 $4,739.3 
(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 16, "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 non-jurisdictional transmission assets. Amounts included in Corporate and Other primarily relate to products and services revenue.
Nine months ended September 30, 2024
(in millions)
Columbia OperationsNIPSCO OperationsCorporate and OtherTotal
Gas Distribution
Residential$1,257.2 $357.5 $— $1,614.7 
Commercial395.6 134.0 — $529.6 
Industrial105.1 56.3 — $161.4 
Off-system30.5 — — $30.5 
Wholesale1.1 — — $1.1 
Miscellaneous(1)
15.4 12.5 — $27.9 
Subtotal$1,804.9 $560.3 $— $2,365.2 
Electric Generation and Power Delivery
Residential$— $498.6 $— $498.6 
Commercial— 470.0 — $470.0 
Industrial— 360.4 — $360.4 
Wholesale— 32.4 — $32.4 
Public Authority— 6.0 — $6.0 
Miscellaneous(1)
— 10.6 — $10.6 
Subtotal$— $1,378.0 $— $1,378.0 
Total Customer Revenues(2)
1,804.9 1,938.3 — 3,743.2 
Other Revenues(3)
59.6 63.9 0.6 124.1 
Total Operating Revenues$1,864.5 $2,002.2 $0.6 $3,867.3 
(1)Amounts included in Columbia Operations 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 16, "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 non-jurisdictional transmission assets.
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 September 30, 2025 and December 31, 2024 are presented in the table below. We had no significant contract assets or liabilities during the period. 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, 2024$525.1 $408.1 
Balance as of September 30, 2025$444.6 $219.5 
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 collectibility. 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, energy consumption trends, revenue projections, actual charge-offs data, recoveries data, shut-offs, customer delinquencies, final bill data, and inflation. 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. A rollforward of our allowance for credit losses as of September 30, 2025 and December 31, 2024 are presented in the table below:

(in millions)
Columbia Operations
NIPSCO Operations
Corporate and OtherTotal
Balance as of December 31, 2024$9.8 $13.9 $— $23.7 
Current period provisions26.2 10.2 — 36.4 
Write-offs charged against allowance(39.7)(9.2)— (48.9)
Recoveries of amounts previously written off6.7 0.7 — 7.4 
Balance as of September 30, 2025$3.0 $15.6 $— $18.6 
(in millions)
Columbia Operations
NIPSCO Operations
Corporate and OtherTotal
Balance as of December 31, 2023$10.2 $11.9 $0.8 $22.9 
Current period provisions26.7 12.1 — 38.8 
Write-offs charged against allowance(43.9)(11.0)(0.8)(55.7)
Recoveries of amounts previously written off16.8 0.9 — 17.7 
Balance as of December 31, 2024$9.8 $13.9 $— $23.7 
v3.25.3
Earnings Per Share
 9 Months Ended
Sep. 30, 2025
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
September 30,		Nine Months Ended
September 30,
(in millions, except per share amounts)2025202420252024
Numerator:
Net Income Available to Common Shareholders
$94.7 $85.7 $671.7 $515.8 
Less: Income allocated to participating securities0.3 0.2 1.4 0.9 
Net Income Available to Common Shareholders - Basic
94.4 85.5 670.3 514.9 
Net Income Available to Common Shareholders - Diluted
$94.4 $85.5 $670.3 $514.9 
Denominator:
Average common shares outstanding - Basic472.1 451.9 471.1 449.4 
Dilutive potential common shares:
Shares contingently issuable under employee stock plans1.0 0.9 1.1 0.9 
Shares restricted under employee stock plans0.4 0.3 0.5 0.3 
ATM forward sale agreements
0.2 1.4 0.1 0.8 
Average Common Shares - Diluted473.7 454.5 472.8 451.4 
Earnings per common share:
Basic$0.20 $0.19 1.421.15
Diluted$0.20 $0.19 1.421.14
v3.25.3
Equity
 9 Months Ended
Sep. 30, 2025
Equity [Abstract]  
Equity Equity
ATM Program. In February 2024, we entered into eight separate equity distribution agreements pursuant to which we are able to sell up to an aggregate of $900.0 million of our common stock.
In February 2025, we executed a forward sale agreement, which allowed 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 2,000,000 shares from third parties, which the forward purchaser sold, through its affiliated agent, at a weighted average price of $40.10 per share. In September 2025, we settled the forward sale agreement in shares for $80.0 million, based on a net price of $40.02 per share.
In March 2025, we executed a forward sale agreement, which allowed 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 1,707,320 shares from third parties, which the forward purchaser sold, through its affiliated agent, at a weighted average price of $41.00 per share. In September 2025, we settled the forward sale agreement in shares for $69.9 million, based on a net price of $40.92 per share.
In June 2025, we executed a forward sale agreement, which allowed 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 2,518,393 shares from third parties, which the forward purchaser sold, through its affiliated agent, at a weighted average price of $39.71 per share. In September 2025, we settled the forward sale agreement in shares for $99.1 million, based on a net price of $39.36 per share.
As of September 30, 2025, the ATM program had approximately $47.5 million of capacity available. The program expires on December 31, 2025.

Series B and B-1 Preferred Stock. On March 15, 2024, we redeemed all 20,000 outstanding shares of Series B Preferred Stock for a redemption price of $25,000 per share and all 20,000 outstanding shares of Series B-1 Preferred Stock for a redemption price of $0.01 per share or $500.0 million in total.
There were no dividends declared per share for the Series B Preferred Stock during the three months ended September 30, 2025 and 2024. Dividends declared per share for the Series B Preferred Stock were zero and $406.25 during the nine months ended September 30, 2025 and 2024, respectively.
v3.25.3
Regulatory Matters
 9 Months Ended
Sep. 30, 2025
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 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).
Renewable generation filings. In February 2025, NIPSCO filed a petition with the IURC to modify its February 2023 order that approved a power purchase agreement related to Templeton and allow for NIPSCO to fully own Templeton. The IURC issued an order on September 24, 2025 approving the filed petition.
GenCo filing. In January 2025, GenCo, an indirect subsidiary of NiSource Inc., filed a declination of jurisdiction petition with the IURC related to the ownership, development, financing, construction and operation of generation facilities. This is an administrative filing and is a step in NIPSCO’s effort to set up a framework to accommodate megaload customers, including data centers. A settlement agreement among GenCo, NIPSCO, and a coalition of NIPSCO's largest industrial customers was approved by the IURC on September 24, 2025. In October 2025, the Indiana Office of the Utility Consumer Counselor ("OUCC") filed a limited Request for Rehearing with the IURC. Subsequently, the OUCC filed a Notice of Appeal of the IURC order approving the GenCo settlement, which was immediately stayed by the Court of Appeals to allow the IURC process to be completed.

NIPSCO Electric rate case filing. On February 7, 2025, NIPSCO and certain intervening parties filed a Joint Stipulation and Settlement Agreement with the IURC. The IURC issued an order on June 26, 2025, approving the Settlement Agreement without modification. New rates were implemented in multiple steps beginning in July 2025 and will continue with the final step no later than March 2026.
v3.25.3
Risk Management Activities
 9 Months Ended
Sep. 30, 2025
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:
September 30, 2025December 31, 2024
(in millions)Assets LiabilitiesAssetsLiabilities
Current(1)
Derivatives not designated as hedging instruments$10.5 $2.8 $9.1 $2.3 
Total$10.5 $2.8 $9.1 $2.3 
Noncurrent(2)
Derivatives not designated as hedging instruments$12.8 $3.7 $17.9 $1.2 
Total$12.8 $3.7 $17.9 $1.2 
(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 and deferred credits", 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 September 30, 2025. If the above gross asset and liability positions were presented net of amounts owed or receivable from counterparties, we would report a net asset position of $16.8 million and $23.5 million at September 30, 2025 and December 31, 2024, 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 on behalf of 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. At September 30, 2025 and December 31, 2024, we had 89.4 MMDth and 77.8 MMDth, respectively, of net energy derivative volumes outstanding related to our natural gas hedges.
NIPSCO has received approval for a program 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 September 30, 2025, the remaining terms of these instruments range from one to seven 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)September 30, 2025December 31, 2024
Regulatory Assets
Losses on commodity price risk programs$10.9 $6.5 
Regulatory Liabilities
Gains on commodity price risk programs23.8 28.7 
Our derivative instruments measured at fair value as of September 30, 2025 and December 31, 2024 do not contain any credit-risk-related contingent features.
Derivatives Designated as Hedging Instruments

Interest rate risk management. As of September 30, 2025 and December 31, 2024 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 nine months ended September 30, 2025 and 2024 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 15, "Accumulated Other Comprehensive Loss," for additional information.
v3.25.3
Fair Value
 9 Months Ended
Sep. 30, 2025
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 September 30, 2025 and December 31, 2024. As of September 30, 2025 and December 31, 2024, 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
September 30, 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
September 30, 2025
Assets
U.S. Treasury debt securities(1)
$4.0 $— $— $4.0 
Risk management assets— 23.3 — 23.3 
Available-for-sale debt securities— 159.0 — 159.0 
Equity securities(2)(3)
$8.5 $— $— $8.5 
Total$12.5 $182.3 $— $194.8 
Liabilities
Risk management liabilities$— $6.5 $— $6.5 
Total$— $6.5 $— $6.5 
(1)Treasury bills are presented in "Cash and cash equivalents" and "Restricted cash" on the Consolidated Balance Sheets.
(2)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 Consolidated Balance Sheets.
(3)As of September 30, 2025, the investment cost of equity securities measured at fair value was $7.9 million, gross unrealized gains were $0.6 million, and the fair value was $8.5 million.


Recurring Fair Value Measurements
December 31, 2024 (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, 2024
Assets
U.S. Treasury debt securities(1)
$80.1 $— $— $80.1 
Risk management assets— 27.0 — 27.0 
Available-for-sale debt securities— 86.7 — 86.7 
Total$80.1 $113.7 $— $193.8 
Liabilities
Risk management liabilities$— $3.5 $— $3.5 
Total$— $3.5 $— $3.5 
(1)Treasury bills are presented in "Cash and cash equivalents" and "Restricted cash" on the Consolidated Balance Sheets.

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.
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 September 30, 2025 and December 31, 2024 were: 
September 30, 2025 (in millions)
Amortized
Cost		Gross Unrealized Gains
Gross Unrealized Losses(1)
Allowance for Credit LossesFair
Value
Available-for-sale debt securities
U.S. Treasury debt securities10.6 $— $— $— $10.6 
Corporate/Other debt securities$149.8 $2.3 $(3.6)$(0.1)$148.4 
Total$160.4 $2.3 $(3.6)$(0.1)$159.0 
December 31, 2024 (in millions)
Amortized
Cost		Gross Unrealized Gains
Gross Unrealized Losses(2)
Allowance for Credit LossesFair
Value
Available-for-sale debt securities
Corporate/Other debt securities$91.9 $0.5 $(5.6)$(0.1)$86.7 
Total$91.9 $0.5 $(5.6)$(0.1)$86.7 
(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 $1.5 million and $55.9 million at September 30, 2025.
(2)Fair value of Corporate/Other debt securities in an unrealized loss position without an allowance for credit losses is $70.1 million at December 31, 2024.
The cost of maturities sold is based upon specific identification. Net realized gains and losses on available-for-sale securities were de minimis and $0.1 million for the three and nine months ended September 30, 2025, respectively, and $0.1 million and $0.5 million for the three and nine months ended September 30, 2024.
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 September 30, 2025, the Company holds $17.9 million of equity investments measured at net asset value.
Non-recurring Fair Value Measurements
We measure the fair value of certain assets, primarily 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.
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 September 30, 2025, 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
September 30, 2025
Estimated Fair
Value as of
September 30, 2025
Carrying
Amount as of
Dec. 31, 2024
Estimated Fair
Value as of
Dec. 31, 2024
Long-term debt (including current portion)$14,503.4 $14,050.3 $13,355.7 $12,505.2 
v3.25.3
Income Taxes
 9 Months Ended
Sep. 30, 2025
Income Tax Disclosure [Abstract]  
Income Taxes
Our interim effective tax rates reflect the estimated annual effective tax rates for 2025 and 2024 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 September 30, 2025 and 2024 were 16.1% and 14.1%, respectively. The effective tax rates for the nine months ended September 30, 2025 and 2024 were 17.0% and 15.4%, 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 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 2.0% in 2025 compared to 2024 is primarily driven by changes in net income attributable to noncontrolling interest, lower AFUDC equity and increases to other permanent differences, partially offset by lower state income taxes.

The increase in the nine month effective tax rate of 1.6% in 2025 compared to 2024 is primarily driven by lower AFUDC equity and changes in net income attributable to noncontrolling interest.

As of September 30, 2025, 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, 2024, for a discussion of these unrecognized tax benefits.
On July 4, 2025, President Donald J. Trump enacted the One Big Beautiful Bill Act ("OBBBA"), which introduced significant federal tax and spending reforms. After evaluation, management determined that the OBBBA does not currently have a material effect on the Company’s financial statements. The Company will continue to monitor the bill’s implementation and will update its financial disclosures as needed should material impacts arise under applicable accounting standards.
v3.25.3
Pension And Other Postretirement Benefits
 9 Months Ended
Sep. 30, 2025
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 nine months ended September 30, 2025 and 2024, we contributed $1.5 million and $1.9 million, respectively, to our pension plans and $15.4 million and $18.3 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 nine months ended September 30, 2025 and 2024:
Pension BenefitsOPEB
Three Months Ended September 30, (in millions)
2025202420252024
Components of Net Periodic Benefit Cost(1)
Service cost$4.9 $5.5 $1.0 $1.3 
Interest cost16.0 16.3 5.6 5.5 
Expected return on assets(23.1)(23.8)(4.2)(4.0)
Amortization of prior service credit— — (0.4)(0.4)
Recognized actuarial loss6.4 7.2 0.4 0.8 
Settlement loss5.6 5.9 — — 
Total Net Periodic Benefit Cost $9.8 $11.1 $2.4 $3.2 
(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).
Pension BenefitsOPEB
Nine Months Ended September 30, (in millions)
2025202420252024
Components of Net Periodic Benefit Cost(1)
Service cost$14.7 $16.4 $3.0 $3.9 
Interest cost48.0 48.9 16.8 16.4 
Expected return on assets(69.3)(71.4)(12.6)(12.0)
Amortization of prior service credit— — (1.2)(1.2)
Recognized actuarial loss19.2 21.6 1.2 2.4 
Settlement loss5.6 5.9 — — 
Total Net Periodic Benefit Cost $18.2 $21.4 $7.2 $9.5 
(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).
During the three months ended September 30, 2025, one of our qualified pension plans met the requirement for settlement accounting. A one-time settlement charge of $5.6 million was recorded during the three months ended September 30, 2025.
In August 2025, we communicated to plan participants of one of our OPEB plans the intention to move from a group self-insured Medicare supplemental health plan to a Sponsored Health Reimbursement Account, with eligible retirees electing coverage through a Healthcare Exchange. This change will become effective on January 1, 2026. Given the intention of the plan and communication to participants, this was considered a plan amendment at the time of communication. This plan amendment triggered remeasurement of this plan, resulting in a decrease to the OPEB regulatory asset of $5.7 million, a decrease to OPEB
liability of $23.3 million, and an increase to accumulated other comprehensive loss of $17.6 million. Net periodic OPEB benefit cost for 2025 decreased by $1.7 million as a result of the interim remeasurement.
In line with the remeasurement, key inputs, economic assumptions, and demographic assumptions changed to calculate the updated OPEB benefit obligation and the net periodic benefit cost at the interim remeasurement date for the plan that triggered settlement accounting. For remeasurement, we used a weighted-average discount rate of 5.53%, a weighted-average health care trend rate of 9.97% for next year and ultimate trend rate of 4.75% to be reached in 2034, and weighted-average expected return on assets of 6.88%.
v3.25.3
Variable Interest Entities
 9 Months Ended
Sep. 30, 2025
Variable Interest Entities [Abstract]  
Variable Interest Entities
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 the managing member and operator of two solar JVs, Indiana Crossroads Solar and Dunns 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 have reached 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 commercially operational JV.
We did not provide any financial or other support during the quarter that was not contractually required.
Our Condensed Consolidated Balance Sheets (unaudited) included the following assets and liabilities associated with VIEs.
(in millions)September 30, 2025December 31, 2024
Net property, plant and equipment
$1,284.4 $1,323.8 
Current assets59.6 65.0 
Total assets(1)
1,344.0 1,388.8 
Current liabilities54.4 53.7 
Asset retirement obligations55.0 58.3 
Finance lease obligations
40.2 40.4 
Total liabilities(1)(2)
$149.6 $152.4 
(1)The assets of each consolidated VIE can only be used 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 September 30, 2025.
Voting Interest Entities. We retain a controlling financial interest in NIPSCO Holdings II and its subsidiaries and consolidate their financial results. 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
September 30,		Nine Months Ended
September 30,
(in millions)
2025202420252024
Contributions from NIPSCO minority interest holders$11.0 $39.8 $145.3 $99.5 
Distributions to NIPSCO minority interest holders
11.1 11.8 55.5 32.0 
v3.25.3
Short-Term Borrowings
 9 Months Ended
Sep. 30, 2025
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 program limit of $1.85 billion and is comprised of a syndicate of banks. We had no outstanding borrowings under this facility as of September 30, 2025 and December 31, 2024.
Commercial Paper Program. Our commercial paper program has a program limit of $1.85 billion. We had $1,060.0 million and $604.6 million of commercial paper outstanding with weighted-average interest rates of 4.40% and 4.73% as of September 30, 2025 and December 31, 2024, 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 May 2026 and October 2026 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 September 30, 2025, the maximum amount of debt that could be borrowed related to our accounts receivable programs was $245.0 million.
We had $200.0 million and no short-term borrowings related to the securitization transactions as of September 30, 2025 and December 31, 2024, respectively.
For the nine months ended September 30, 2025 and 2024, $200.0 million and $(337.6) million, respectively, were recorded as cash flows from (used for) financing activities 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 their maturities are less than 90 days.
v3.25.3
Other Commitments And Contingencies
 9 Months Ended
Sep. 30, 2025
Commitments and Contingencies Disclosure [Abstract]  
Commitments and Contingencies Guarantees and Indemnities. We and certain of our subsidiaries enter into various agreements providing financial or performance assurance to third parties on behalf of certain subsidiaries as a part of normal business. Such agreements include guarantees and stand-by letters of credit. These agreements are entered into primarily to support or enhance the creditworthiness otherwise attributed to a subsidiary on a stand-alone basis, thereby facilitating the extension of sufficient credit to accomplish the subsidiaries' intended commercial purposes. As of September 30, 2025 and December 31, 2024, we had issued letters of credit of $119.0 million and $9.4 million, respectively, for the benefit of third parties.
We provide guarantees related to our future performance under BTAs for our renewable generation projects. At September 30, 2025 and December 31, 2024, our guarantees for multiple BTAs totaled $29.2 million and $1,127.5 million, respectively. The amount of each guaranty will decrease upon the substantial completion of the construction of the facilities. See ''- D. Other Matters - Generation Transition,'' below for more information.
We provide guarantees related to some of our rail and pipeline service agreements. As of September 30, 2025 and December 31, 2024, if we do not meet our contractual obligations under the terms of these agreements we would be required to pay up to a maximum of $52.0 million and $61.7 million, respectively.
B. Legal Proceedings. From time to time, various legal and regulatory claims and proceedings are pending or threatened against the Company and its subsidiaries. While the amounts claimed may be substantial, the Company is unable to predict with certainty the ultimate outcome of such claims and proceedings. The Company establishes reserves whenever it believes it to be appropriate for pending litigation matters. However, the actual results of resolving the pending litigation matters may be substantially higher than the amounts reserved. If one or more matters were decided against us, the effects could be material to our results of operations in the period in which we would be required to record or adjust the related liability and could also be material to our cash flows in the periods that we would be required to pay such liability. Due to the inherent uncertainty of litigation, there can be no assurance that the resolution of any particular claim, proceeding or investigation would not have a material adverse effect on our results of operations, financial position or liquidity.
Other Claims and Proceedings. We are also party to other claims, regulatory and legal proceedings arising in the ordinary course of business in each state in which we have operations, and based upon an investigation of these matters and discussion with legal counsel, we believe the ultimate outcome of such other legal proceedings to be individually, or in aggregate, not material at this time.
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 September 30, 2025 and December 31, 2024, we had recorded a liability of $84.6 million and $91.8 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 51 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, 2025. Our total estimated liability related to the facilities subject to remediation was $77.3 million and $86.4 million at September 30, 2025 and December 31, 2024, respectively. The liability represents our best estimate of the probable cost to remediate the MGP sites. Our model indicates that it is reasonably possible that remediation costs could vary by as much as $16.5 million and $16.3 million at September 30, 2025 and December 31, 2024, respectively, in addition to the costs noted above. 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.

On May 8, 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. In the second quarter of 2025, we accrued an additional $38.8 million to cover probable and estimable compliance activities associated with the Legacy CCR Rule. 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.
Generation Transition. NIPSCO has executed several BTAs with developers to construct renewable generation facilities. In October 2024, NIPSCO contracted with a developer to convert the previously approved Templeton PPA to a BTA and in February 2025 filed a CPCN with the IURC seeking approval of the full ownership BTA structure. In September 2025, the IURC granted NIPSCO a CPCN to acquire Templeton through the full ownership BTA structure. NIPSCO's purchase obligation under Templeton is dependent on timely completion of construction. Certain agreements require NIPSCO to make partial payments upon the developer's completion of significant construction milestones.
In January 2025, the Fairbanks project achieved mechanical completion, resulting in NIPSCO making a $336.6 million payment to the developer. In May 2025, the Fairbanks project achieved substantial completion, resulting in NIPSCO making a $141.4 million payment to the developer in June 2025.
In January 2025, the Dunns Bridge II project achieved substantial completion, resulting in NIPSCO making a $217.6 million payment to the developer in February 2025.
In June 2025, the Gibson project achieved mechanical completion, resulting in NIPSCO making a $262.4 million payment to the developer. In August 2025, the Gibson project achieved substantial completion, resulting in NIPSCO making a $133.7 million payment to the developer in September 2025.
EPC Agreements. GenCo has entered into certain EPC contracts to construct generation capacity assets to support the Data Center Contract, requiring payments at specified periods. The assets contemplated by these contracts are subject to IURC approval. We may terminate for convenience the EPC Contracts and pay certain incurred project costs and termination fees if the Data Center Contract is terminated or IURC approval of the underlying assets is not obtained.
v3.25.3
Accumulated Other Comprehensive Loss
 9 Months Ended
Sep. 30, 2025
Other Comprehensive Income (Loss), Tax [Abstract]  
Accumulated Other Comprehensive Loss
The following tables display the components of Accumulated Other Comprehensive Loss, net of tax:
(in millions)
Gains and Losses on Securities(1)
Gains and Losses on Cash Flow Hedges(1)
Pension and OPEB Items(1)
Accumulated
Other
Comprehensive
Loss(1)
Balance as of June 30, 2025$(2.2)$(13.4)$(12.6)$(28.2)
Other comprehensive income before reclassifications
1.3 — 13.8 15.1 
Amounts reclassified from accumulated other comprehensive loss— (0.1)0.2 0.1 
Net current-period other comprehensive income (loss)
1.3 (0.1)14.0 15.2 
Balance as of September 30, 2025$(0.9)$(13.5)$1.4 $(13.0)
(1)All amounts are net of tax. Amounts in parentheses indicate debits.
(in millions)
Gains and Losses on Securities(1)
Gains and Losses on Cash Flow Hedges(1)
Pension and OPEB Items(1)
Accumulated
Other
Comprehensive
Loss(1)
Balance as of December 31, 2024$(4.0)$(13.2)$(13.2)$(30.4)
Other comprehensive income before reclassifications
3.1 — 13.9 17.0 
Amounts reclassified from accumulated other comprehensive loss— (0.3)0.7 0.4 
Net current-period other comprehensive income (loss)3.1 (0.3)14.6 17.4 
Balance as of September 30, 2025$(0.9)$(13.5)$1.4 $(13.0)
(1)All amounts are net of tax. Amounts in parentheses indicate debits.
(in millions)
Gains and Losses on Securities(1)
Gains and Losses on Cash Flow Hedges(1)
Pension and OPEB Items(1)
Accumulated
Other
Comprehensive
Loss(1)
Balance as of June 30, 2024$(7.6)$(13.0)$(13.0)$(33.6)
Other comprehensive income (loss) before reclassifications
3.5 0.4 (0.1)3.8 
Amounts reclassified from accumulated other comprehensive loss— (0.5)0.7 0.2 
Net current-period other comprehensive income (loss)3.5 (0.1)0.6 4.0 
Balance as of September 30, 2024$(4.1)$(13.1)$(12.4)$(29.6)
(1)All amounts are net of tax. Amounts in parentheses indicate debits.
(in millions)
Gains and Losses on Securities(1)
Gains and Losses on Cash Flow Hedges(1)
Pension and OPEB Items(1)
Accumulated
Other
Comprehensive
Loss(1)
Balance as of December 31, 2023$(7.3)$(12.8)$(13.5)$(33.6)
Other comprehensive income (loss) before reclassifications2.8 — (0.1)2.7 
Amounts reclassified from accumulated other comprehensive loss0.4 (0.3)1.2 1.3 
Net current-period other comprehensive income (loss)3.2 (0.3)1.1 4.0 
Balance as of September 30, 2024$(4.1)$(13.1)$(12.4)$(29.6)
(1)All amounts are net of tax. Amounts in parentheses indicate debits.
v3.25.3
Other, Net
 9 Months Ended
Sep. 30, 2025
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
September 30,		Nine Months Ended
September 30,
(in millions)2025202420252024
Interest income$3.8 $3.4 $7.3 $7.8 
AFUDC equity8.5 32.1 26.3 56.7 
Pension and other postretirement non-service cost
(5.7)(5.9)(11.1)(10.2)
Tax penalties
5.3 (0.5)(3.9)(0.5)
Miscellaneous
(2.0)0.1 (2.4)(2.4)
Total Other, net$9.9 $29.2 $16.2 $51.4 
v3.25.3
Business Segment Information
 9 Months Ended
Sep. 30, 2025
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. 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 September 30, 2025
(in millions)
Columbia Operations
NIPSCO Operations
Total of Reportable Segments
Operating Revenues
External Revenue
$484.9 $787.0 $1,271.9 
Intersegment Revenue
3.3 0.3 3.6 
Total Operating Revenue$488.2 $787.3 $1,275.5 
Cost of energy
58.5 135.2 193.7 
O&M
212.8 215.1 427.9 
Depreciation
112.7 185.3 298.0 
Total other taxes
52.019.171.1 
Other segment items(1)
0.1 — 0.1 
Operating Income$52.1 $232.6 $284.7 
(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.
Three Months Ended September 30, 2024
(in millions)
Columbia Operations
NIPSCO Operations
Total of Reportable Segments
Operating Revenues
External Revenue
$423.4 $652.6 $1,076.0 
Intersegment Revenue
3.3 0.3 3.6 
Total Operating Revenue426.7 652.9 1,079.6 
Cost of energy
34.2 131.7 165.9 
O&M
202.9 177.7 380.6 
Depreciation
103.0 156.8 259.8 
Total other taxes
45.415.460.8
Operating Income$41.2 $171.3 $212.5 

Nine Months Ended September 30, 2025
(in millions)
Columbia Operations
NIPSCO Operations
Total of Reportable Segments
Operating Revenues
External Revenue
$2,326.7 $2,409.0 $4,735.7 
Intersegment Revenue
10.0 0.8 10.8 
Total Operating Revenue$2,336.7 $2,409.8 $4,746.5 
Cost of energy
548.7 554.3 1,103.0 
O&M
663.5 628.1 1,291.6 
Depreciation
332.6 492.5 825.1 
Total other taxes
171.455.7227.1 
Other segment items(1)
0.4 0.7 1.1 
Operating Income$620.1 $678.5 $1,298.6 
(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.
Nine Months Ended September 30, 2024
(in millions)
Columbia Operations
NIPSCO Operations
Total of Reportable Segments
Operating Revenues
External Revenue
$1,864.5 $2,002.2 $3,866.7 
Intersegment Revenue
9.6 0.8 10.4 
Total Operating Revenue1,874.1 2,003.0 3,877.1 
Cost of energy
319.3 436.3 755.6 
O&M
604.9 556.5 1,161.4 
Depreciation
300.6 432.5 733.1 
Total other taxes
149.547.8197.3
Other segment items(1)
— (0.1)(0.1)
Operating Income$499.8 $530.0 $1,029.8 
(1)Other segment items consists of (Gain) 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)September 30,
2025		December 31,
2024
Assets
Columbia Operations
$15,267.9 $14,769.5 
NIPSCO Operations
17,834.8 15,823.5 
Corporate and Other
1,300.2 1,195.1 
Consolidated Assets
$34,402.9 $31,788.1 


To reconcile the segment tables above to consolidated NiSource:
Three Months Ended September 30, 2025
(in millions)
Total Reportable Segments
Corporate and Other
Eliminations
Consolidated NiSource
Total Operating Revenue
$1,275.5 $151.8 $(154.2)$1,273.1 
Operating Income
284.7 12.8 — 297.5 

Three Months Ended September 30, 2024
(in millions)Total Reportable SegmentsCorporate and OtherEliminations
Consolidated NiSource
Total Operating Revenue
$1,079.6 $145.9 $(149.2)$1,076.3 
Operating Income
212.5 5.8 — 218.3 
Nine Months Ended September 30, 2025
(in millions)
Total Reportable Segments
Corporate and Other
Eliminations
Consolidated NiSource
Total Operating Revenue
$4,746.5 $441.8 $(449.0)$4,739.3 
Operating Income
1,298.6 21.2 — 1,319.8 

Nine Months Ended September 30, 2024
(in millions)Total Reportable SegmentsCorporate and OtherEliminations
Consolidated NiSource
Total Operating Revenue
$3,877.1 $425.1 $(434.9)$3,867.3 
Operating Income
1,029.8 8.9 — 1,038.7 
v3.25.3
Supplemental Disclosures of Cash Flow Information
 9 Months Ended
Sep. 30, 2025
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):
Nine Months Ended
September 30,
(in millions)20252024
Accounts receivable
$263.3 $290.0 
Inventories
(86.2)101.3 
Accounts payable
(223.5)(182.6)
Customer deposits and credits
4.6 (32.8)
Taxes accrued
7.3 (31.0)
Interest accrued
40.9 11.0 
Exchange gas receivable/payable
59.8 (161.6)
Other accruals
(20.4)(17.8)
Prepayments and other current assets
(45.4)(61.2)
Accrued compensation and employee benefits
(26.4)(1.1)
Total change in working capital
$(26.0)$(85.8)
Nine Months Ended
September 30,
(in millions)
20252024
Non-cash transactions:
Capital expenditures included in current liabilities$408.2 $348.0 
Dividends declared but not paid137.4 125.3 
v3.25.3
Subsequent Event
 9 Months Ended
Sep. 30, 2025
Subsequent Events [Abstract]  
Subsequent Event
Minority Equity Interest Sale

On October 28, 2025, NiSource issued a 19.9% indirect equity interest in NiSource’s wholly-owned subsidiary GenCo to BIP Orion Holdco L.P. and BIP Orion Holdco II L.P., affiliates of Blackstone (collectively, “Investor”), in exchange for $35.2 million. On October 28, 2025, simultaneously with issuance of the 19.9% indirect equity interest in GenCo, Investor, Generation Holdings I, Generation Holdings II and NiSource entered into an Amended and Restated Limited Liability Company Agreement of Generation Holdings II (the “LLC Agreement”).

The LLC Agreement establishes, among other things, governance rights, exit rights, requirements for additional capital contributions, mechanics for distributions, and other arrangements for Generation Holdings II. Specifically, under the terms of the LLC Agreement, Investor will provide up to $1.325 billion in additional capital contributions over a seven-year period, which obligation is backed by an Equity Commitment Letter from Blackstone or an affiliate thereof. Under the LLC Agreement, Investor is entitled to appoint two directors to the board of directors of Generation Holdings II (the “Board”) so long as Investor (together with any approved affiliate) holds at least a 17.5% Percentage Interest (as defined in the LLC Agreement). Investor is expected to appoint two directors to the Board, such that the Board will be comprised of seven directors, two appointed by Investor and five appointed by NiSource. The LLC Agreement also contains certain investor protections, including, among other things, requiring Investor approval for Generation Holdings II to take certain major actions. In addition, the LLC Agreement contains certain terms surrounding transfer rights and other obligations applicable to both Investor and NiSource. Under the LLC Agreement, Generation Holdings II has agreed that, so long as Investor holds a 14.9% or greater Percentage Interest in Generation Holdings II, Generation Holdings II, NIPSCO Holdings II (as defined below) and/or their respective subsidiaries will be the exclusive vehicles for all power, storage and generation requirements for data center customers within NIPSCO’s service territory.
On October 28, 2025, the members of NIPSCO Holdings II entered into a Third Amended and Restated Limited Liability Company Agreement of NIPSCO Holdings II (the "Amended LLC Agreement"), which, among other changes, increased the amount and time period for additional mandatory capital contributions required to be contributed by Investor by $175 million and seven years, which obligation is backed by an Equity Commitment Letter from Blackstone or an affiliate thereof, and amended certain provisions to facilitate NIPSCO Holdings II and its subsidiaries’ provision of electric service to data center customers (and related activities) and their related contracts and arrangements with Generation Holdings II and its subsidiaries.
v3.25.3
Accounting Changes and Error Corrections (Policies)
 9 Months Ended
Sep. 30, 2025
Accounting Changes and Error Corrections [Abstract]  
New Accounting Pronouncements, Policy
Recently Issued Accounting Pronouncements
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. This pronouncement updates the guidance on capitalization of internal-use software, including removing the development stages utilized for evaluation of when certain activities are capital eligible. The ASU instead provides that an entity is required to start capitalizing eligible software development costs when (1) management has authorized and committed to funding the software project and (2) it is probable that the project will be completed and the software will be used to perform the function intended, which is referred to as the “probable-to-complete recognition threshold”. This probable-to-complete threshold includes an evaluation of whether there is significant uncertainty associated with the development activities of the software. The ASU is effective for fiscal years beginning after December 15, 2027. We are currently evaluating the impacts this amendment will have on our internal-use software capitalization policy.

In November 2024, the FASB issued ASU 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40). This pronouncement requires disaggregated disclosure of income statement expenses for public business entities. The ASU requires disclosure in tabular format of disaggregation of relevant expense captions presented on the income statement by certain natural expense categories with certain related qualitative disclosures within the notes to the financial statements. The ASU does not change the expense captions an entity presents on the income statement. The ASU is effective for fiscal years beginning after December 15, 2026, and interim reporting periods within annual reporting periods beginning after December 15, 2027, as defined in ASU 2025-01, 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.

In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. This pronouncement enhances required income tax disclosures. The pronouncement will require disclosure of specific categories and reconciling items included in the rate reconciliation, disaggregation between federal, state and local income taxes paid, and disclosure of income taxes paid by jurisdictions over a certain threshold. Additionally, the pronouncement eliminates certain required disclosures related to unrecognized tax benefits. This ASU is effective for annual periods beginning after December 15, 2024, with early adoption permitted, and is to be applied on a prospective basis with retrospective application permitted. We will implement and provide the required disclosures in our Annual Report on Form 10-K for the year ended December 31, 2025.
Recently Adopted Accounting Pronouncements
In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. This pronouncement enhances annual and interim disclosure requirements over reportable segments, primarily through enhanced disclosures about significant segment expenses. Specifically, the pronouncement requires disclosure of significant segment expenses that are regularly provided to the CODM and included within each reported measure of segment profit or loss, disclosure of an amount for other segment items representing the difference between segment revenue and segment expenses already disclosed, disclosure of all required annual disclosures for interim periods and disclosure of title and
position of the CODM and how the CODM uses reported measures. The pronouncement also allows for more than one measure of segment profit if the CODM uses more than one measure in assessing segment performance. This pronouncement was effective for annual periods beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. NiSource adopted this pronouncement as of December 31, 2024, with retrospective application and updated its disclosures to include significant expenses regularly provided to the CODM, the CODM's title and how the CODM utilizes reported measures. See Note 16, "Business Segment Information," for further discussion.
v3.25.3
Revenue Recognition (Tables)
 9 Months Ended
Sep. 30, 2025
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 September 30, 2025
(in millions)
Columbia OperationsNIPSCO OperationsCorporate and OtherTotal
Gas Distribution
Residential$328.1 $72.9 $— $401.0 
Commercial95.1 32.2 — 127.3 
Industrial36.0 19.7 — 55.7 
Off-system13.8 — — 13.8 
Miscellaneous(1)
6.7 2.6 — 9.3 
Subtotal$479.7 $127.4 $— $607.1 
Electric Generation and Power Delivery
Residential$— $254.6 $— $254.6 
Commercial— 210.6 — 210.6 
Industrial— 156.2 — 156.2 
Wholesale— 18.4 — 18.4 
Miscellaneous(1)
— (6.7)— (6.7)
Subtotal $— $633.1 $— $633.1 
Total Customer Revenues(2)
479.7 760.5 — 1,240.2 
Other Revenues(3)
5.2 26.5 1.2 32.9 
Total Operating Revenues$484.9 $787.0 $1.2 $1,273.1 
(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 16, "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 non-jurisdictional transmission assets. Amounts included in Corporate and Other primarily relate to products and services revenue.
Three months ended September 30, 2024
(in millions)
Columbia Operations
NIPSCO Operations
Corporate and OtherTotal
Gas Distribution
Residential$296.9 $66.8 $— $363.7 
Commercial78.3 28.6 — 106.9 
Industrial32.0 16.4 — 48.4 
Off-system7.1 — — 7.1 
Wholesale0.1 — — 0.1 
Miscellaneous(1)
2.9 1.9 — 4.8 
Subtotal$417.3 $113.7 $— $531.0 
Electric Generation and Power Delivery
Residential$— $197.9 $— $197.9 
Commercial— 172.7 — 172.7 
Industrial— 124.8 — 124.8 
Wholesale— 15.0 — 15.0 
Public Authority— 2.0 — 2.0 
Miscellaneous(1)
— 2.7 — 2.7 
Subtotal$— $515.1 $— $515.1 
Total Customer Revenues(2)
417.3 628.8 — 1,046.1 
Other Revenues(3)
6.1 23.8 0.3 30.2 
Total Operating Revenues$423.4 $652.6 $0.3 $1,076.3 
(1)Amounts included in Columbia Operations 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 16, "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 non-jurisdictional transmission assets.
Nine months ended September 30, 2025
(in millions)
Columbia OperationsNIPSCO OperationsCorporate and OtherTotal
Gas Distribution
Residential$1,576.3 $478.5 $— $2,054.8 
Commercial527.8 180.8 — $708.6 
Industrial121.5 73.7 — $195.2 
Off-system58.9 — — $58.9 
Miscellaneous(1)
27.4 10.6 — $38.0 
Subtotal$2,311.9 $743.6 $— $3,055.5 
Electric Generation and Power Delivery
Residential$— $586.4 $— $586.4 
Commercial— 531.7 — $531.7 
Industrial— 432.3 — $432.3 
Wholesale— 37.9 — $37.9 
Miscellaneous(1)
— (7.6)— $(7.6)
Subtotal$— $1,580.7 $— $1,580.7 
Total Customer Revenues(2)
2,311.9 2,324.3 — 4,636.2 
Other Revenues(3)
14.8 84.7 3.6 103.1 
Total Operating Revenues$2,326.7 $2,409.0 $3.6 $4,739.3 
(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 16, "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 non-jurisdictional transmission assets. Amounts included in Corporate and Other primarily relate to products and services revenue.
Nine months ended September 30, 2024
(in millions)
Columbia OperationsNIPSCO OperationsCorporate and OtherTotal
Gas Distribution
Residential$1,257.2 $357.5 $— $1,614.7 
Commercial395.6 134.0 — $529.6 
Industrial105.1 56.3 — $161.4 
Off-system30.5 — — $30.5 
Wholesale1.1 — — $1.1 
Miscellaneous(1)
15.4 12.5 — $27.9 
Subtotal$1,804.9 $560.3 $— $2,365.2 
Electric Generation and Power Delivery
Residential$— $498.6 $— $498.6 
Commercial— 470.0 — $470.0 
Industrial— 360.4 — $360.4 
Wholesale— 32.4 — $32.4 
Public Authority— 6.0 — $6.0 
Miscellaneous(1)
— 10.6 — $10.6 
Subtotal$— $1,378.0 $— $1,378.0 
Total Customer Revenues(2)
1,804.9 1,938.3 — 3,743.2 
Other Revenues(3)
59.6 63.9 0.6 124.1 
Total Operating Revenues$1,864.5 $2,002.2 $0.6 $3,867.3 
(1)Amounts included in Columbia Operations 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 16, "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 non-jurisdictional transmission assets.
Customer Accounts Receivable The balances of customer receivables as of September 30, 2025 and December 31, 2024 are presented in the table below. We had no significant contract assets or liabilities during the period. 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, 2024$525.1 $408.1 
Balance as of September 30, 2025$444.6 $219.5 
Accounts Receivable, Allowance for Credit Loss A rollforward of our allowance for credit losses as of September 30, 2025 and December 31, 2024 are presented in the table below:

(in millions)
Columbia Operations
NIPSCO Operations
Corporate and OtherTotal
Balance as of December 31, 2024$9.8 $13.9 $— $23.7 
Current period provisions26.2 10.2 — 36.4 
Write-offs charged against allowance(39.7)(9.2)— (48.9)
Recoveries of amounts previously written off6.7 0.7 — 7.4 
Balance as of September 30, 2025$3.0 $15.6 $— $18.6 
(in millions)
Columbia Operations
NIPSCO Operations
Corporate and OtherTotal
Balance as of December 31, 2023$10.2 $11.9 $0.8 $22.9 
Current period provisions26.7 12.1 — 38.8 
Write-offs charged against allowance(43.9)(11.0)(0.8)(55.7)
Recoveries of amounts previously written off16.8 0.9 — 17.7 
Balance as of December 31, 2024$9.8 $13.9 $— $23.7 
v3.25.3
Earnings Per Share (Tables)
 9 Months Ended
Sep. 30, 2025
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
September 30,		Nine Months Ended
September 30,
(in millions, except per share amounts)2025202420252024
Numerator:
Net Income Available to Common Shareholders
$94.7 $85.7 $671.7 $515.8 
Less: Income allocated to participating securities0.3 0.2 1.4 0.9 
Net Income Available to Common Shareholders - Basic
94.4 85.5 670.3 514.9 
Net Income Available to Common Shareholders - Diluted
$94.4 $85.5 $670.3 $514.9 
Denominator:
Average common shares outstanding - Basic472.1 451.9 471.1 449.4 
Dilutive potential common shares:
Shares contingently issuable under employee stock plans1.0 0.9 1.1 0.9 
Shares restricted under employee stock plans0.4 0.3 0.5 0.3 
ATM forward sale agreements
0.2 1.4 0.1 0.8 
Average Common Shares - Diluted473.7 454.5 472.8 451.4 
Earnings per common share:
Basic$0.20 $0.19 1.421.15
Diluted$0.20 $0.19 1.421.14
v3.25.3
Risk Management Activities (Tables)
 9 Months Ended
Sep. 30, 2025
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:
September 30, 2025December 31, 2024
(in millions)Assets LiabilitiesAssetsLiabilities
Current(1)
Derivatives not designated as hedging instruments$10.5 $2.8 $9.1 $2.3 
Total$10.5 $2.8 $9.1 $2.3 
Noncurrent(2)
Derivatives not designated as hedging instruments$12.8 $3.7 $17.9 $1.2 
Total$12.8 $3.7 $17.9 $1.2 
(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 and deferred credits", 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)September 30, 2025December 31, 2024
Regulatory Assets
Losses on commodity price risk programs$10.9 $6.5 
Regulatory Liabilities
Gains on commodity price risk programs23.8 28.7 
Our derivative instruments measured at fair value as of September 30, 2025 and December 31, 2024 do not contain any credit-risk-related contingent features.
v3.25.3
Fair Value (Tables)
 9 Months Ended
Sep. 30, 2025
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 September 30, 2025 and December 31, 2024. As of September 30, 2025 and December 31, 2024, 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
September 30, 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
September 30, 2025
Assets
U.S. Treasury debt securities(1)
$4.0 $— $— $4.0 
Risk management assets— 23.3 — 23.3 
Available-for-sale debt securities— 159.0 — 159.0 
Equity securities(2)(3)
$8.5 $— $— $8.5 
Total$12.5 $182.3 $— $194.8 
Liabilities
Risk management liabilities$— $6.5 $— $6.5 
Total$— $6.5 $— $6.5 
(1)Treasury bills are presented in "Cash and cash equivalents" and "Restricted cash" on the Consolidated Balance Sheets.
(2)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 Consolidated Balance Sheets.
(3)As of September 30, 2025, the investment cost of equity securities measured at fair value was $7.9 million, gross unrealized gains were $0.6 million, and the fair value was $8.5 million.


Recurring Fair Value Measurements
December 31, 2024 (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, 2024
Assets
U.S. Treasury debt securities(1)
$80.1 $— $— $80.1 
Risk management assets— 27.0 — 27.0 
Available-for-sale debt securities— 86.7 — 86.7 
Total$80.1 $113.7 $— $193.8 
Liabilities
Risk management liabilities$— $3.5 $— $3.5 
Total$— $3.5 $— $3.5 
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 September 30, 2025 and December 31, 2024 were: 
September 30, 2025 (in millions)
Amortized
Cost		Gross Unrealized Gains
Gross Unrealized Losses(1)
Allowance for Credit LossesFair
Value
Available-for-sale debt securities
U.S. Treasury debt securities10.6 $— $— $— $10.6 
Corporate/Other debt securities$149.8 $2.3 $(3.6)$(0.1)$148.4 
Total$160.4 $2.3 $(3.6)$(0.1)$159.0 
December 31, 2024 (in millions)
Amortized
Cost		Gross Unrealized Gains
Gross Unrealized Losses(2)
Allowance for Credit LossesFair
Value
Available-for-sale debt securities
Corporate/Other debt securities$91.9 $0.5 $(5.6)$(0.1)$86.7 
Total$91.9 $0.5 $(5.6)$(0.1)$86.7 
(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 $1.5 million and $55.9 million at September 30, 2025.
(2)Fair value of Corporate/Other debt securities in an unrealized loss position without an allowance for credit losses is $70.1 million at December 31, 2024.
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
September 30, 2025
Estimated Fair
Value as of
September 30, 2025
Carrying
Amount as of
Dec. 31, 2024
Estimated Fair
Value as of
Dec. 31, 2024
Long-term debt (including current portion)$14,503.4 $14,050.3 $13,355.7 $12,505.2 
v3.25.3
Pension And Other Postretirement Benefits (Tables)
 9 Months Ended
Sep. 30, 2025
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 nine months ended September 30, 2025 and 2024:
Pension BenefitsOPEB
Three Months Ended September 30, (in millions)
2025202420252024
Components of Net Periodic Benefit Cost(1)
Service cost$4.9 $5.5 $1.0 $1.3 
Interest cost16.0 16.3 5.6 5.5 
Expected return on assets(23.1)(23.8)(4.2)(4.0)
Amortization of prior service credit— — (0.4)(0.4)
Recognized actuarial loss6.4 7.2 0.4 0.8 
Settlement loss5.6 5.9 — — 
Total Net Periodic Benefit Cost $9.8 $11.1 $2.4 $3.2 
(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).
v3.25.3
Variable Interest Entities (Tables)
 9 Months Ended
Sep. 30, 2025
Variable Interest Entities [Abstract]  
Variable Interest Entities Assets and Liabilities
Our Condensed Consolidated Balance Sheets (unaudited) included the following assets and liabilities associated with VIEs.
(in millions)September 30, 2025December 31, 2024
Net property, plant and equipment
$1,284.4 $1,323.8 
Current assets59.6 65.0 
Total assets(1)
1,344.0 1,388.8 
Current liabilities54.4 53.7 
Asset retirement obligations55.0 58.3 
Finance lease obligations
40.2 40.4 
Total liabilities(1)(2)
$149.6 $152.4 
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
September 30,		Nine Months Ended
September 30,
(in millions)
2025202420252024
Contributions from NIPSCO minority interest holders$11.0 $39.8 $145.3 $99.5 
Distributions to NIPSCO minority interest holders
11.1 11.8 55.5 32.0 
v3.25.3
Accumulated Other Comprehensive Loss (Tables)
 9 Months Ended
Sep. 30, 2025
Other Comprehensive Income (Loss), Tax [Abstract]  
Components Of Accumulated Other Comprehensive Loss
The following tables display the components of Accumulated Other Comprehensive Loss, net of tax:
(in millions)
Gains and Losses on Securities(1)
Gains and Losses on Cash Flow Hedges(1)
Pension and OPEB Items(1)
Accumulated
Other
Comprehensive
Loss(1)
Balance as of June 30, 2025$(2.2)$(13.4)$(12.6)$(28.2)
Other comprehensive income before reclassifications
1.3 — 13.8 15.1 
Amounts reclassified from accumulated other comprehensive loss— (0.1)0.2 0.1 
Net current-period other comprehensive income (loss)
1.3 (0.1)14.0 15.2 
Balance as of September 30, 2025$(0.9)$(13.5)$1.4 $(13.0)
(1)All amounts are net of tax. Amounts in parentheses indicate debits.
(in millions)
Gains and Losses on Securities(1)
Gains and Losses on Cash Flow Hedges(1)
Pension and OPEB Items(1)
Accumulated
Other
Comprehensive
Loss(1)
Balance as of December 31, 2024$(4.0)$(13.2)$(13.2)$(30.4)
Other comprehensive income before reclassifications
3.1 — 13.9 17.0 
Amounts reclassified from accumulated other comprehensive loss— (0.3)0.7 0.4 
Net current-period other comprehensive income (loss)3.1 (0.3)14.6 17.4 
Balance as of September 30, 2025$(0.9)$(13.5)$1.4 $(13.0)
(1)All amounts are net of tax. Amounts in parentheses indicate debits.
(in millions)
Gains and Losses on Securities(1)
Gains and Losses on Cash Flow Hedges(1)
Pension and OPEB Items(1)
Accumulated
Other
Comprehensive
Loss(1)
Balance as of June 30, 2024$(7.6)$(13.0)$(13.0)$(33.6)
Other comprehensive income (loss) before reclassifications
3.5 0.4 (0.1)3.8 
Amounts reclassified from accumulated other comprehensive loss— (0.5)0.7 0.2 
Net current-period other comprehensive income (loss)3.5 (0.1)0.6 4.0 
Balance as of September 30, 2024$(4.1)$(13.1)$(12.4)$(29.6)
(1)All amounts are net of tax. Amounts in parentheses indicate debits.
(in millions)
Gains and Losses on Securities(1)
Gains and Losses on Cash Flow Hedges(1)
Pension and OPEB Items(1)
Accumulated
Other
Comprehensive
Loss(1)
Balance as of December 31, 2023$(7.3)$(12.8)$(13.5)$(33.6)
Other comprehensive income (loss) before reclassifications2.8 — (0.1)2.7 
Amounts reclassified from accumulated other comprehensive loss0.4 (0.3)1.2 1.3 
Net current-period other comprehensive income (loss)3.2 (0.3)1.1 4.0 
Balance as of September 30, 2024$(4.1)$(13.1)$(12.4)$(29.6)
(1)All amounts are net of tax. Amounts in parentheses indicate debits.
v3.25.3
Other, Net (Tables)
 9 Months Ended
Sep. 30, 2025
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
September 30,		Nine Months Ended
September 30,
(in millions)2025202420252024
Interest income$3.8 $3.4 $7.3 $7.8 
AFUDC equity8.5 32.1 26.3 56.7 
Pension and other postretirement non-service cost
(5.7)(5.9)(11.1)(10.2)
Tax penalties
5.3 (0.5)(3.9)(0.5)
Miscellaneous
(2.0)0.1 (2.4)(2.4)
Total Other, net$9.9 $29.2 $16.2 $51.4 
v3.25.3
Business Segment Information (Tables)
 9 Months Ended
Sep. 30, 2025
Segment Reporting [Abstract]  
Schedule Of Operating Income Derived From Revenues And Expenses By Segment
Three Months Ended September 30, 2025
(in millions)
Columbia Operations
NIPSCO Operations
Total of Reportable Segments
Operating Revenues
External Revenue
$484.9 $787.0 $1,271.9 
Intersegment Revenue
3.3 0.3 3.6 
Total Operating Revenue$488.2 $787.3 $1,275.5 
Cost of energy
58.5 135.2 193.7 
O&M
212.8 215.1 427.9 
Depreciation
112.7 185.3 298.0 
Total other taxes
52.019.171.1 
Other segment items(1)
0.1 — 0.1 
Operating Income$52.1 $232.6 $284.7 
(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.
Three Months Ended September 30, 2024
(in millions)
Columbia Operations
NIPSCO Operations
Total of Reportable Segments
Operating Revenues
External Revenue
$423.4 $652.6 $1,076.0 
Intersegment Revenue
3.3 0.3 3.6 
Total Operating Revenue426.7 652.9 1,079.6 
Cost of energy
34.2 131.7 165.9 
O&M
202.9 177.7 380.6 
Depreciation
103.0 156.8 259.8 
Total other taxes
45.415.460.8
Operating Income$41.2 $171.3 $212.5 

Nine Months Ended September 30, 2025
(in millions)
Columbia Operations
NIPSCO Operations
Total of Reportable Segments
Operating Revenues
External Revenue
$2,326.7 $2,409.0 $4,735.7 
Intersegment Revenue
10.0 0.8 10.8 
Total Operating Revenue$2,336.7 $2,409.8 $4,746.5 
Cost of energy
548.7 554.3 1,103.0 
O&M
663.5 628.1 1,291.6 
Depreciation
332.6 492.5 825.1 
Total other taxes
171.455.7227.1 
Other segment items(1)
0.4 0.7 1.1 
Operating Income$620.1 $678.5 $1,298.6 
(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.
Nine Months Ended September 30, 2024
(in millions)
Columbia Operations
NIPSCO Operations
Total of Reportable Segments
Operating Revenues
External Revenue
$1,864.5 $2,002.2 $3,866.7 
Intersegment Revenue
9.6 0.8 10.4 
Total Operating Revenue1,874.1 2,003.0 3,877.1 
Cost of energy
319.3 436.3 755.6 
O&M
604.9 556.5 1,161.4 
Depreciation
300.6 432.5 733.1 
Total other taxes
149.547.8197.3
Other segment items(1)
— (0.1)(0.1)
Operating Income$499.8 $530.0 $1,029.8 
(1)Other segment items consists of (Gain) 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)September 30,
2025		December 31,
2024
Assets
Columbia Operations
$15,267.9 $14,769.5 
NIPSCO Operations
17,834.8 15,823.5 
Corporate and Other
1,300.2 1,195.1 
Consolidated Assets
$34,402.9 $31,788.1 


To reconcile the segment tables above to consolidated NiSource:
Three Months Ended September 30, 2025
(in millions)
Total Reportable Segments
Corporate and Other
Eliminations
Consolidated NiSource
Total Operating Revenue
$1,275.5 $151.8 $(154.2)$1,273.1 
Operating Income
284.7 12.8 — 297.5 

Three Months Ended September 30, 2024
(in millions)Total Reportable SegmentsCorporate and OtherEliminations
Consolidated NiSource
Total Operating Revenue
$1,079.6 $145.9 $(149.2)$1,076.3 
Operating Income
212.5 5.8 — 218.3 
Nine Months Ended September 30, 2025
(in millions)
Total Reportable Segments
Corporate and Other
Eliminations
Consolidated NiSource
Total Operating Revenue
$4,746.5 $441.8 $(449.0)$4,739.3 
Operating Income
1,298.6 21.2 — 1,319.8 
v3.25.3
Supplemental Disclosures of Cash Flow Information (Tables)
 9 Months Ended
Sep. 30, 2025
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):
Nine Months Ended
September 30,
(in millions)20252024
Accounts receivable
$263.3 $290.0 
Inventories
(86.2)101.3 
Accounts payable
(223.5)(182.6)
Customer deposits and credits
4.6 (32.8)
Taxes accrued
7.3 (31.0)
Interest accrued
40.9 11.0 
Exchange gas receivable/payable
59.8 (161.6)
Other accruals
(20.4)(17.8)
Prepayments and other current assets
(45.4)(61.2)
Accrued compensation and employee benefits
(26.4)(1.1)
Total change in working capital
$(26.0)$(85.8)
Nine Months Ended
September 30,
(in millions)
20252024
Non-cash transactions:
Capital expenditures included in current liabilities$408.2 $348.0 
Dividends declared but not paid137.4 125.3 
v3.25.3
Revenue Recognition (Narrative) (Details) - USD ($)
$ in Millions
 9 Months Ended 12 Months Ended
Sep. 30, 2025
Dec. 31, 2024
Dec. 31, 2023
Revenue from Contract with Customer [Abstract]      
Accounts Receivable, Allowance for Credit Loss $ 18.6 $ 23.7 $ 22.9
Current period provisions 36.4 38.8  
Write-offs charged against allowance (48.9) (55.7)  
Recoveries of amounts previously written off $ 7.4 $ 17.7  
v3.25.3
Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($)
 3 Months Ended 9 Months Ended
Jun. 12, 2025
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Disaggregation of Revenue [Line Items]          
Customer revenues   $ 1,240,200,000 $ 1,046,100,000 $ 4,636,200,000 $ 3,743,200,000
Other revenues   32,900,000 30,200,000 103,100,000 124,100,000
Total Operating Revenues   1,273,100,000 1,076,300,000 4,739,300,000 3,867,300,000
NiSource Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues   607,100,000 531,000,000.0 3,055,500,000 2,365,200,000
NiSource Electric Generation and Power Delivery          
Disaggregation of Revenue [Line Items]          
Customer revenues   633,100,000 515,100,000 1,580,700,000 1,378,000,000
Corporate and Other          
Disaggregation of Revenue [Line Items]          
Customer revenues $ 2,518,393 0 0 0 0
Other revenues   1,200,000 300,000 3,600,000 600,000
Corporate and Other | Unaffiliated          
Disaggregation of Revenue [Line Items]          
Revenues   1,200,000 300,000 3,600,000 600,000
NIPSCO Operations          
Disaggregation of Revenue [Line Items]          
Customer revenues   760,500,000 628,800,000 2,324,300,000 1,938,300,000
Other revenues   26,500,000 23,800,000 84,700,000 63,900,000
Total Operating Revenues   787,000,000.0 652,600,000    
NIPSCO Operations | Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues   127,400,000 113,700,000 743,600,000 560,300,000
NIPSCO Operations | NIPSCO Electric Generation          
Disaggregation of Revenue [Line Items]          
Customer revenues   633,100,000 515,100,000 1,580,700,000 1,378,000,000
NIPSCO Operations | Unaffiliated          
Disaggregation of Revenue [Line Items]          
Revenues       2,409,000,000 2,002,200,000
Columbia Operations          
Disaggregation of Revenue [Line Items]          
Customer revenues   479,700,000 417,300,000 2,311,900,000 1,804,900,000
Other revenues   5,200,000 6,100,000 14,800,000 59,600,000
Columbia Operations | Unaffiliated          
Disaggregation of Revenue [Line Items]          
Revenues       2,326,700,000 1,864,500,000
Residential | NiSource Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues   401,000,000.0 363,700,000 2,054,800,000 1,614,700,000
Residential | NiSource Electric Generation and Power Delivery          
Disaggregation of Revenue [Line Items]          
Customer revenues   254,600,000 197,900,000 586,400,000 498,600,000
Residential | Corporate and Other          
Disaggregation of Revenue [Line Items]          
Customer revenues   0 0 0 0
Residential | NIPSCO Operations | Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues   72,900,000 66,800,000 478,500,000 357,500,000
Residential | NIPSCO Operations | NIPSCO Electric Generation          
Disaggregation of Revenue [Line Items]          
Customer revenues   254,600,000 197,900,000 586,400,000 498,600,000
Residential | Columbia Operations          
Disaggregation of Revenue [Line Items]          
Customer revenues   328,100,000 296,900,000 1,576,300,000 1,257,200,000
Commercial | NiSource Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues   127,300,000 106,900,000 708,600,000 529,600,000
Commercial | NiSource Electric Generation and Power Delivery          
Disaggregation of Revenue [Line Items]          
Customer revenues   210,600,000 172,700,000 531,700,000 470,000,000.0
Commercial | Corporate and Other          
Disaggregation of Revenue [Line Items]          
Customer revenues   0 0 0 0
Commercial | NIPSCO Operations | Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues   32,200,000 28,600,000 180,800,000 134,000,000.0
Commercial | NIPSCO Operations | NIPSCO Electric Generation          
Disaggregation of Revenue [Line Items]          
Customer revenues   210,600,000 172,700,000 531,700,000 470,000,000.0
Commercial | Columbia Operations          
Disaggregation of Revenue [Line Items]          
Customer revenues   95,100,000 78,300,000 527,800,000 395,600,000
Industrial | NiSource Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues   55,700,000 48,400,000 195,200,000 161,400,000
Industrial | NiSource Electric Generation and Power Delivery          
Disaggregation of Revenue [Line Items]          
Customer revenues   156,200,000 124,800,000 432,300,000 360,400,000
Industrial | Corporate and Other          
Disaggregation of Revenue [Line Items]          
Customer revenues   0 0 0 0
Industrial | NIPSCO Operations | Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues   19,700,000 16,400,000 73,700,000 56,300,000
Industrial | NIPSCO Operations | NIPSCO Electric Generation          
Disaggregation of Revenue [Line Items]          
Customer revenues   156,200,000 124,800,000 432,300,000 360,400,000
Industrial | Columbia Operations          
Disaggregation of Revenue [Line Items]          
Customer revenues   36,000,000.0 32,000,000.0 121,500,000 105,100,000
Off-system | NiSource Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues   13,800,000 7,100,000 58,900,000 30,500,000
Off-system | Corporate and Other          
Disaggregation of Revenue [Line Items]          
Customer revenues   0 0 0 0
Off-system | NIPSCO Operations | Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues   0 0 0 0
Off-system | Columbia Operations          
Disaggregation of Revenue [Line Items]          
Customer revenues   13,800,000 7,100,000 58,900,000 30,500,000
Miscellaneous | NiSource Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues   9,300,000 4,800,000 38,000,000.0 27,900,000
Miscellaneous | NiSource Electric Generation and Power Delivery          
Disaggregation of Revenue [Line Items]          
Customer revenues   (6,700,000) 2,700,000 (7,600,000) 10,600,000
Miscellaneous | Corporate and Other          
Disaggregation of Revenue [Line Items]          
Customer revenues   0 0 0 0
Miscellaneous | NIPSCO Operations | Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues   2,600,000 1,900,000 10,600,000 12,500,000
Miscellaneous | NIPSCO Operations | NIPSCO Electric Generation          
Disaggregation of Revenue [Line Items]          
Customer revenues   (6,700,000) 2,700,000 (7,600,000) 10,600,000
Miscellaneous | Columbia Operations          
Disaggregation of Revenue [Line Items]          
Customer revenues   6,700,000 2,900,000 27,400,000 15,400,000
Wholesale | NiSource Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues     100,000   1,100,000
Wholesale | NiSource Electric Generation and Power Delivery          
Disaggregation of Revenue [Line Items]          
Customer revenues   18,400,000 15,000,000.0 37,900,000 32,400,000
Wholesale | Corporate and Other          
Disaggregation of Revenue [Line Items]          
Customer revenues     0   0
Wholesale | NIPSCO Operations | Gas Distribution          
Disaggregation of Revenue [Line Items]          
Customer revenues     0   0
Wholesale | NIPSCO Operations | NIPSCO Electric Generation          
Disaggregation of Revenue [Line Items]          
Customer revenues   $ 18,400,000 15,000,000.0 $ 37,900,000 32,400,000
Wholesale | Columbia Operations          
Disaggregation of Revenue [Line Items]          
Customer revenues     100,000   1,100,000
Public Authority          
Disaggregation of Revenue [Line Items]          
Customer revenues     2,000,000.0   6,000,000.0
Public Authority | NIPSCO Operations | NIPSCO Electric Generation          
Disaggregation of Revenue [Line Items]          
Customer revenues     $ 2,000,000.0   $ 6,000,000.0
v3.25.3
Revenue Recognition (Customer Accounts Receivable) (Details) - USD ($)
$ in Millions
Sep. 30, 2025
Dec. 31, 2024
Revenue from Contract with Customer [Abstract]    
Customer Accounts Receivable, Billed (Less Reserve) $ 444.6 $ 525.1
Customer Accounts Receivable, Unbilled (Less Reserve) $ 219.5 $ 408.1
v3.25.3
Revenue Recognition Revenue Recognition (Allowance for Credit Losses) (Details) - USD ($)
 9 Months Ended 12 Months Ended
Sep. 30, 2025
Dec. 31, 2024
Dec. 31, 2023
Accounts Receivable Allowance For Credit Loss [Line Items]      
Accounts Receivable, Allowance for Credit Loss $ 18,600,000 $ 23,700,000 $ 22,900,000
Current period provisions 36,400,000 38,800,000  
Write-offs charged against allowance 48,900,000 55,700,000  
Recoveries of amounts previously written off 7,400,000 17,700,000  
Corporate and Other      
Accounts Receivable Allowance For Credit Loss [Line Items]      
Accounts Receivable, Allowance for Credit Loss 0 0 800,000
Current period provisions 0 0  
Write-offs charged against allowance 0 (800,000)  
Recoveries of amounts previously written off 0 0  
Columbia Operations      
Accounts Receivable Allowance For Credit Loss [Line Items]      
Accounts Receivable, Allowance for Credit Loss 3,000,000.0 9,800,000 10,200,000
Current period provisions 26,200,000 26,700,000  
Write-offs charged against allowance 39,700,000 43,900,000  
Recoveries of amounts previously written off 6,700,000 16,800,000  
NIPSCO Operations      
Accounts Receivable Allowance For Credit Loss [Line Items]      
Accounts Receivable, Allowance for Credit Loss 15,600,000 13,900,000 $ 11,900,000
Current period provisions 10,200,000 12,100,000  
Write-offs charged against allowance 9,200,000 11,000,000.0  
Recoveries of amounts previously written off $ 700,000 $ 900,000  
v3.25.3
Earnings Per Share (Schedule of Earnings Per Share, Basic and Diluted) (Details) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Numerator        
Net Income Available to Common Shareholders $ 94.7 $ 85.7 $ 671.7 $ 515.8
Undistributed Earnings (Loss) Allocated to Participating Securities, Basic 0.3 0.2 1.4 0.9
Net Income Available to Common Shareholders - Basic Excluding Participating Securities 94.4 85.5 670.3 514.9
Net Income Available to Common Shareholders - Diluted $ 94.4 $ 85.5 $ 670.3 $ 514.9
Denominator        
Basic Average Common Shares Outstanding 472.1 451.9 471.1 449.4
Dilutive potential common shares        
Shares contingently issuable under employee stock plans 1.0 0.9 1.1 0.9
Shares restricted under stock plans 0.4 0.3 0.5 0.3
ATM forward sale agreements 0.2 1.4 0.1 0.8
Diluted Average Common Shares 473.7 454.5 472.8 451.4
Basic Earnings Per Share $ 0.20 $ 0.19 $ 1.42 $ 1.15
Diluted Earnings Per Share $ 0.20 $ 0.19 $ 1.42 $ 1.14
v3.25.3
Equity (Narrative) (Details) - USD ($)
 3 Months Ended 9 Months Ended
Jun. 12, 2025
Mar. 03, 2025
Feb. 27, 2025
Feb. 22, 2024
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Mar. 15, 2024
Preferred Stock, Par or Stated Value Per Share                 $ 25,000
Preferred Stock Shares Redeemed         6,226,000 18,148,000 6,226,000 18,148,000  
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share $ 39.71 $ 41.00 $ 40.10            
Preferred Stock Redemption Premium         $ 0 $ 0 $ 0 $ 14,000,000.0  
Customer revenues         1,240,200,000 1,046,100,000 4,636,200,000 3,743,200,000  
Corporate and Other                  
Customer revenues $ 2,518,393       $ 0 $ 0 0 0  
Forward March 03                  
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share         $ 40.92        
Forward February 22                  
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share         40.02        
Forward June 12                  
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share         $ 39.36        
Pension Plan                  
Defined Benefit Plan, Plan Assets, Contributions by Employer             1,500,000 1,900,000  
Other Postretirement Benefit Plan                  
Defined Benefit Plan, Plan Assets, Contributions by Employer             15,400,000 $ 18,300,000  
At The Market Program                  
Common Stock Aggregate Sale Price       $ 900,000,000.0          
ATM Program Equity Remaining Available for Issuance             $ 47,500,000    
Forward February 22                  
Common Stock Aggregate Sale Price     $ 80,000,000            
Forward Contract Indexed to Issuer's Equity, Shares     2,000,000            
Forward March 03                  
Common Stock Aggregate Sale Price         $ 69,900,000        
Forward Contract Indexed to Issuer's Equity, Shares   1,707,320              
Forward June 12                  
Common Stock Aggregate Sale Price         $ 99,100,000        
Series B Preferred Stock [Member]                  
Preferred Stock, Dividends Per Share, Declared             $ 0 $ 406.25  
Series B-1 Preferred Stock                  
Preferred Stock, Par or Stated Value Per Share                 $ 0.01
Preferred Stock, Redemption Amount                 $ 500,000,000
Preferred Stock, Shares Issued                 20,000
v3.25.3
Equity Schedule of Stock by Class - Preferred (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Jun. 30, 2025
Dec. 31, 2024
Mar. 15, 2024
Dec. 31, 2023
Class of Stock [Line Items]                
Shares outstanding $ 9,118.2   $ 9,118.2     $ 8,684.2    
Preferred Stock Shares Redeemed 6,226 18,148 6,226 18,148        
Series B Preferred Stock [Member]                
Class of Stock [Line Items]                
Dividends Declared Per Share     $ 0 $ 406.25        
Series B-1 Preferred Stock                
Class of Stock [Line Items]                
Preferred Stock, Redemption Amount             $ 500.0  
Preferred Stock, Redemption Amount             $ 500.0  
Preferred Stock                
Class of Stock [Line Items]                
Preferred Stock, Shares Outstanding 0 0 0 0 0 0   40
v3.25.3
Equity Schedule of Series A Equity Units (Details) - $ / shares
 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Series B Preferred Stock [Member]    
Schedule of Series A Equity Units [Line Items]    
Preferred Stock, Dividends Per Share, Declared $ 0 $ 406.25
v3.25.3
Regulatory Matters (Narrative) (Details)
Sep. 30, 2025
MW
Rosewater  
Public Utilities, General Disclosures [Line Items]  
Nameplate Capacity 102
v3.25.3
Risk Management Activities (Narrative) (Details)
mMDth in Millions, $ in Millions
Sep. 30, 2025
USD ($)
mMDth
Dec. 31, 2024
USD ($)
mMDth
Derivative [Line Items]    
Limit of GCA Volumes 20.00%  
Derivative Asset, Subject to Master Netting Arrangement, after Offset | $ $ 16.8 $ 23.5
Customer annual demand 2000.00%  
Minimum    
Derivative [Line Items]    
Commodity Contract Length 1 year  
Maximum    
Derivative [Line Items]    
Commodity Contract Length 7 years  
Natural Gas    
Derivative [Line Items]    
Derivative, Nonmonetary Notional Amount | mMDth 89.4 77.8
v3.25.3
Risk Management Activities (Schedule of Derivative Instruments in Statement of Financial Position, Fair Value) (Details) - USD ($)
$ in Millions
Sep. 30, 2025
Dec. 31, 2024
Risk Management Assets Current    
Derivatives, Fair Value [Line Items]    
Risk management assets $ 10.5 $ 9.1
Risk Management Assets Noncurrent    
Derivatives, Fair Value [Line Items]    
Risk management assets 12.8 17.9
Risk Management Liabilities Current    
Derivatives, Fair Value [Line Items]    
Risk management liabilities 2.8 2.3
Risk Management Liabilities Noncurrent    
Derivatives, Fair Value [Line Items]    
Risk management liabilities 3.7 1.2
Commodity Price Risk Programs | Risk Management Assets Current    
Derivatives, Fair Value [Line Items]    
Risk management assets 10.5 9.1
Commodity Price Risk Programs | Risk Management Assets Noncurrent    
Derivatives, Fair Value [Line Items]    
Risk management assets 12.8 17.9
Commodity Price Risk Programs | Risk Management Liabilities Current    
Derivatives, Fair Value [Line Items]    
Risk management liabilities 2.8 2.3
Commodity Price Risk Programs | Risk Management Liabilities Noncurrent    
Derivatives, Fair Value [Line Items]    
Risk management liabilities $ 3.7 $ 1.2
v3.25.3
Risk Management Activities (Schedule of Gains (Losses) on Commodity Price Risk Programs) (Details) - USD ($)
Sep. 30, 2025
Dec. 31, 2024
Derivative Instruments, Gain (Loss) [Line Items]    
Regulatory Assets $ 5.7  
Regulatory Liabilities 23.3  
Deferred Derivative Gain (Loss)    
Derivative Instruments, Gain (Loss) [Line Items]    
Regulatory Liabilities 23,800,000 $ 28,700,000
Deferred Derivative Gain (Loss)    
Derivative Instruments, Gain (Loss) [Line Items]    
Regulatory Assets $ 10,900,000 $ 6,500,000
v3.25.3
Fair Value (Narrative) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended 9 Months Ended
Sep. 30, 2024
Jun. 30, 2025
Sep. 30, 2025
Sep. 30, 2024
Dec. 31, 2024
Fair Value Disclosure [Line Items]          
Transfers between Fair Value Hierarchies   $ 0.0 $ 0.0    
Allowance for Credit Loss     0.1   $ 0.1
Debt Securities, Available-for-Sale, Realized Gain $ 0.1   0.1 $ 0.5  
Debt and Equity Securities, FV-NI [Line Items]          
Equity Securities, FV-NI, Cost     7.9    
Debt and Equity Securities, Unrealized Gain (Loss)     0.6    
Equity Securities, FV-NI     8.5    
Net Assets     17.9    
Net Assets     17.9    
U.S. Treasury debt securities          
Fair Value Disclosure [Line Items]          
Allowance for Credit Loss     0.0    
Corporate/Other debt securities          
Fair Value Disclosure [Line Items]          
Allowance for Credit Loss     $ 0.1   $ 0.1
v3.25.3
Fair Value (Fair Value Of Financial Assets And Liabilities Measured On A Recurring Basis) (Details) - USD ($)
$ in Millions
Sep. 30, 2025
Dec. 31, 2024
Assets    
Available-for-sale, securities $ 159.0 $ 86.7
Equity Securities, FV-NI 8.5  
Total 194.8 193.8
Liabilities    
Total 6.5 3.5
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value 4.0 80.1
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 8.5  
Total 12.5 80.1
Liabilities    
Risk management liabilities 0.0 0.0
Total 0.0 0.0
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value 4.0 80.1
Significant Other Observable Inputs (Level 2)    
Assets    
Risk management assets 23.3 27.0
Available-for-sale, securities 159.0 86.7
Equity Securities, FV-NI 0.0  
Total 182.3 113.7
Liabilities    
Risk management liabilities 6.5 3.5
Total 6.5 3.5
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value 0.0 0.0
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  
Total 0.0 0.0
Liabilities    
Risk management liabilities 0.0 0.0
Total 0.0 0.0
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value 0.0 0.0
Available-for-sale Securities    
Assets    
Available-for-sale, securities 159.0 86.7
Risk management assets    
Assets    
Risk management assets 23.3 27.0
Liabilities    
Risk management liabilities $ 6.5 $ 3.5
v3.25.3
Fair Value (Available-For-Sale Securities) (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Dec. 31, 2024
Fair Value Disclosure [Line Items]        
Amortized Cost   $ 160.4   $ 91.9
Gross Unrealized Gains   2.3   0.5
Gross Unrealized Losses   (3.6)   (5.6)
Allowance for Credit Loss   (0.1)   (0.1)
Fair Value   159.0   86.7
Debt Securities, Available-for-Sale, Realized Gain $ 0.1 0.1 $ 0.5  
U.S. Treasury debt securities        
Fair Value Disclosure [Line Items]        
Amortized Cost   10.6    
Gross Unrealized Gains   0.0    
Gross Unrealized Losses   0.0    
Allowance for Credit Loss   0.0    
Fair Value   10.6    
Corporate/Other debt securities        
Fair Value Disclosure [Line Items]        
Amortized Cost   149.8   91.9
Gross Unrealized Gains   2.3   0.5
Gross Unrealized Losses   (3.6)   (5.6)
Allowance for Credit Loss   (0.1)   (0.1)
Fair Value   148.4   86.7
Debt Securities, Available-for-sale, Unrealized Loss Position   55.9   $ 70.1
US Treasury Securities        
Fair Value Disclosure [Line Items]        
Debt Securities, Available-for-sale, Unrealized Loss Position   $ 1.5    
v3.25.3
Fair Value (Carrying Amount And Estimated Fair Values Of Financial Instruments) (Details) - USD ($)
$ in Millions
Sep. 30, 2025
Dec. 31, 2024
Fair Value Disclosures [Abstract]    
Long-term Debt (including current portion), Carrying Amount $ 14,503.4 $ 13,355.7
Long-term debt (including current portion), Estimated Fair Value $ 14,050.3 $ 12,505.2
v3.25.3
Goodwill (Narrative) (Details) - USD ($)
$ in Millions
Sep. 30, 2025
Dec. 31, 2024
Goodwill [Line Items]    
Goodwill $ 1,485.9 $ 1,485.9
v3.25.3
Goodwill (Schedule of Goodwill) (Details) - USD ($)
$ in Millions
Sep. 30, 2025
Dec. 31, 2024
Goodwill [Line Items]    
Goodwill $ 1,485.9 $ 1,485.9
v3.25.3
Income Taxes (Narrative) (Details)
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Rate
Sep. 30, 2024
Rate
Sep. 30, 2025
Rate
Sep. 30, 2024
Rate
Income Tax Disclosure [Abstract]        
Effective income tax rates 16.10% 14.10% 17.00% 15.40%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate     21.00%  
Increase (Decrease) in Effective Tax Rate 2.00%   1.60%  
v3.25.3
Pension And Other Postretirement Benefits (Narrative) (Details) - USD ($)
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Defined Benefit Plan Disclosure [Line Items]        
Regulatory Assets $ 5.7   $ 5.7  
Postemployment Benefits [Abstract]        
Regulatory Liabilities $ 23.3   23.3  
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Remeasurement due to Settlement     $ 5.6  
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate 475.00%   475.00%  
Defined Benefit Plan, Assumed Health Care Cost Trend Rate, Description     9.97  
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Change Due to Subsequent Interim Measurement, Weighted-Average Expected Long-Term Rate of Return on Plan Assets     688.00%  
Discount rate 553.00%   553.00%  
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement     $ 1.7  
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax     17.6  
Pension Plan        
Defined Benefit Plan Disclosure [Line Items]        
Employer contributions     1,500,000 $ 1,900,000
Postemployment Benefits [Abstract]        
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement $ (5,600,000) $ (5,900,000) (5,600,000) (5,900,000)
Defined Benefit Plan, Expected Return (Loss) on Plan Assets 23,100,000 23,800,000 69,300,000 71,400,000
Other Postretirement Benefit Plan        
Defined Benefit Plan Disclosure [Line Items]        
Employer contributions     15,400,000 18,300,000
Postemployment Benefits [Abstract]        
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement 0 0   0
Defined Benefit Plan, Expected Return (Loss) on Plan Assets $ 4,200,000 $ 4,000,000.0 $ 12,600,000 $ 12,000,000.0
v3.25.3
Pension And Other Postretirement Benefits (Components Of The Plans' Net Periodic Benefits Cost) (Details) - USD ($)
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Defined Benefit Plan Disclosure [Line Items]        
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement     $ (1.7)  
Pension Plan        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost $ 4,900,000 $ 5,500,000 14,700,000 $ 16,400,000
Interest cost 16,000,000.0 16,300,000 48,000,000.0 48,900,000
Expected return on assets (23,100,000) (23,800,000) (69,300,000) (71,400,000)
Amortization of prior service credit 0 0 0 0
Recognized actuarial loss 6,400,000 7,200,000 19,200,000 21,600,000
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement 5,600,000 5,900,000 5,600,000 5,900,000
Total Net Periodic Benefits Cost 9,800,000 11,100,000 18,200,000 21,400,000
Other Postretirement Benefit Plan        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost 1,000,000.0 1,300,000 3,000,000.0 3,900,000
Interest cost 5,600,000 5,500,000 16,800,000 16,400,000
Expected return on assets (4,200,000) (4,000,000.0) (12,600,000) (12,000,000.0)
Amortization of prior service credit (400,000) (400,000) (1,200,000) (1,200,000)
Recognized actuarial loss 400,000 800,000 1,200,000 2,400,000
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement 0 0   0
Total Net Periodic Benefits Cost $ 2,400,000 $ 3,200,000 $ 7,200,000 $ 9,500,000
v3.25.3
Variable Interest Entities (Narrative) (Details)
$ in Millions
 3 Months Ended 9 Months Ended
Jun. 18, 2025
USD ($)
May 31, 2025
USD ($)
Feb. 03, 2025
USD ($)
Jan. 15, 2025
USD ($)
Sep. 30, 2025
USD ($)
Rate
MW
Mar. 31, 2025
USD ($)
Sep. 30, 2024
USD ($)
Sep. 30, 2025
USD ($)
Rate
MW
Sep. 30, 2024
USD ($)
Variable Interest Entity [Line Items]                  
Wind Power Purchase Agreement, Purchase Percentage | Rate         100.00%     100.00%  
Payments to Acquire Assets, Investing Activities | $ $ 262.4 $ 141.4 $ 217.6 $ 336.6          
Income Taxes | $         $ 20.6   $ 15.9 $ 150.1 $ 109.5
Contributions from NIPSCO minority interest holders | $         11.0   39.8 145.3 99.5
Payments to Noncontrolling Interests | $         $ 11.1 $ 32.0 $ 11.8 $ 55.5 $ 32.0
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  
v3.25.3
Variable Interest Entities (Schedule of VIE Assets and Liabilities) (Details) - USD ($)
$ in Millions
Sep. 30, 2025
Dec. 31, 2024
Variable Interest Entity [Line Items]    
Public Utilities, Property, Plant and Equipment, Net [1] $ 28,000.1 $ 25,453.9
Current assets [1] 1,848.2 2,080.2
Other Assets, Noncurrent 4,271.7 4,075.3
Total Assets 34,402.9 31,788.1
Current liabilities [2] 3,533.4 4,113.4
Asset retirement obligations 751.4 698.6
Finance lease obligations 337.4 313.0
Variable Interest Entity, Primary Beneficiary    
Variable Interest Entity [Line Items]    
Finance Lease, Liability, Payment, Due 40.2 40.4
Consolidated Variable Interest Entities    
Variable Interest Entity [Line Items]    
Public Utilities, Property, Plant and Equipment, Net 1,284.4 1,323.8
Current assets 59.6 65.0
Total Assets 1,344.0 1,388.8
Current liabilities 54.4 53.7
Asset retirement obligations 55.0 58.3
Total Liabilities $ 149.6 $ 152.4
[1] Includes $1,284.4 million and $1,323.8 million at September 30, 2025 and December 31, 2024, respectively, of net property, plant and equipment assets and $59.6 million and $65.0 million at September 30, 2025 and December 31, 2024, 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 $54.4 million and $53.7 million at September 30, 2025 and December 31, 2024, respectively, of current liabilities and $55.0 million and $58.3 million at September 30, 2025 and December 31, 2024, respectively, of other liabilities, and finance leases of $40.2 million and $40.4 million at September 30, 2025 and December 31, 2024 respectively, of consolidated VIEs that creditors do not have recourse to our general credit. Refer to Note 4, "Noncontrolling Interests," for additional information.
v3.25.3
Long-Term Debt (Narrative) (Details)
$ in Millions
Aug. 15, 2025
USD ($)
Jun. 27, 2025
USD ($)
Mar. 27, 2025
USD ($)
Sep. 30, 2025
USD ($)
MW
Dec. 31, 2024
USD ($)
Standby Letters of Credit          
Debt Instrument [Line Items]          
Revolving credit facility interest rate of 2.13% at March 31, 2020       $ 119.0 $ 9.4
NiSource          
Debt Instrument [Line Items]          
Senior Notes   $ 900.0      
Rosewater          
Debt Instrument [Line Items]          
Nameplate Capacity | MW       102  
Senior Notes | NiSource          
Debt Instrument [Line Items]          
Senior Notes   $ 750.0 $ 750.0 $ 1,500.0  
Debt, Weighted Average Interest Rate 0.95% 5.85% 5.85%    
Proceeds from Debt, Net of Issuance Costs   $ 1,616.0 $ 739.6    
Maturities of Senior Debt $ 1,250.0        
Unsecured Debt | NiSource          
Debt Instrument [Line Items]          
Debt, Weighted Average Interest Rate   5.35%      
v3.25.3
Short-Term Borrowings (Narrative) (Details)
$ in Millions
 9 Months Ended
Sep. 30, 2025
USD ($)
Sep. 30, 2024
USD ($)
Dec. 31, 2024
USD ($)
Feb. 09, 2024
USD ($)
Short-term Debt [Line Items]        
Short-term debt due to asset securitization $ 200.0   $ 0.0  
Short-term Debt $ 1,260.0   604.6  
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 $ 200.0 $ (337.6)    
Short-term Debt 245.0      
Revolving Credit Facility        
Short-term Debt [Line Items]        
Line of Credit Facility, Maximum Borrowing Capacity 1,850.0      
Long-term Line of Credit 0.0   0.0  
Commercial Paper        
Short-term Debt [Line Items]        
Line of Credit Facility, Maximum Borrowing Capacity       $ 1,850.0
Commercial paper outstanding $ 1,060.0   $ 604.6  
Short-term Debt, Weighted Average Interest Rate, at Point in Time 4.40%   4.73%  
v3.25.3
Other Commitments And Contingencies (Narrative) (Details)
$ in Millions
 3 Months Ended
Oct. 28, 2025
USD ($)
Rate
Sep. 04, 2025
USD ($)
Jun. 18, 2025
USD ($)
May 31, 2025
USD ($)
Feb. 03, 2025
USD ($)
Jan. 15, 2025
USD ($)
Jun. 30, 2025
USD ($)
Sep. 30, 2025
USD ($)
Rate
Dec. 31, 2024
USD ($)
Other Commitments And Contingencies [Line Items]                  
Guaranty Liabilities               $ 29.2 $ 1,127.5
Recorded reserves to cover environmental remediation at various sites               $ 84.6 91.8
Wind Power Purchase Agreement, Purchase Percentage | Rate               100.00%  
Business Combination, Price of Acquisition, Expected $ 35.2                
Payments to Acquire Assets, Investing Activities     $ 262.4 $ 141.4 $ 217.6 $ 336.6      
Contractual Obligation               $ 52.0 61.7
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               51  
Liability for Estimated Remediation Costs               $ 77.3 86.4
Reasonably possible remediation costs variance from reserve               16.5 16.3
CCR Remediation                  
Other Commitments And Contingencies [Line Items]                  
Accrual for Environmental Loss Contingencies, Period Increase (Decrease)             $ 38.8    
Standby Letters of Credit                  
Other Commitments And Contingencies [Line Items]                  
Long-term Line of Credit               $ 119.0 $ 9.4
Payments to Acquire Assets, Investing Activities   $ 133.7              
v3.25.3
Accumulated Other Comprehensive Loss (Components Of Accumulated Other Comprehensive Loss) (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance $ 10,996.9 $ 9,819.6 $ 10,668.3 $ 10,136.3
Other Comprehensive Income (Loss) before reclassifications 15.1 3.8 17.0 2.7
Amounts reclassified from accumulated other comprehensive income (loss) 0.1 0.2 0.4 1.3
Net current-period other comprehensive income (loss) 15.2 4.0 17.4 4.0
Ending balance 11,241.8 10,328.8 11,241.8 10,328.8
Interest Rate Risk        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Net current-period other comprehensive income (loss)     (0.3)  
Accumulated Other Comprehensive Income (Loss)        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (28.2) (33.6) (30.4) (33.6)
Net current-period other comprehensive income (loss) 15.2   17.4  
Ending balance (13.0) (29.6) (13.0) (29.6)
Gains and Losses on Securities        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (2.2) (7.6) (4.0) (7.3)
Other Comprehensive Income (Loss) before reclassifications 1.3 3.5 3.1 2.8
Amounts reclassified from accumulated other comprehensive income (loss) 0.0 0.0 0.0 0.4
Net current-period other comprehensive income (loss) 1.3 3.5 3.1 3.2
Ending balance (0.9) (4.1) (0.9) (4.1)
Gains and Losses on Cash Flow Hedges        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (13.4) (13.0) (13.2) (12.8)
Other Comprehensive Income (Loss) before reclassifications 0.0 0.4 0.0 0.0
Amounts reclassified from accumulated other comprehensive income (loss) (0.1) (0.5) (0.3) (0.3)
Net current-period other comprehensive income (loss) (0.1) (0.1)   (0.3)
Ending balance (13.5) (13.1) (13.5) (13.1)
Pension and OPEB Items        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (12.6) (13.0) (13.2) (13.5)
Other Comprehensive Income (Loss) before reclassifications 13.8 (0.1) 13.9 (0.1)
Amounts reclassified from accumulated other comprehensive income (loss) 0.2 0.7 0.7 1.2
Net current-period other comprehensive income (loss) 14.0 0.6 14.6 1.1
Ending balance $ 1.4 $ (12.4) $ 1.4 $ (12.4)
v3.25.3
Other, Net (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Other, Net [Abstract]        
Accounts receivable $ 3.8 $ 3.4 $ 7.3 $ 7.8
Inventories 8.5 32.1 26.3 56.7
Customer deposits and credits (5.7) (5.9) (11.1) (10.2)
Income Tax Examination, Penalties Expense 5.3 (0.5) (3.9) (0.5)
Other, net 9.9 29.2 16.2 51.4
Miscellaneous Non-Operating Income (Expense) $ (2.0) $ 0.1 $ (2.4) $ (2.4)
v3.25.3
Business Segment Information (Narrative) (Details)
 3 Months Ended
Sep. 30, 2025
segment
Segment Reporting [Abstract]  
Primary business segments 2
v3.25.3
Business Segment Information (Schedule Of Operating Income Derived From Revenues And Expenses By Segment) (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Dec. 31, 2024
Segment Reporting Information [Line Items]          
Consolidated Operating Income (Loss) $ 297.5 $ 218.3 $ 1,319.8 $ 1,038.7  
Total Assets 34,402.9   34,402.9   $ 31,788.1
Regulated Operating Revenue 1,273.1 1,076.3 4,739.3 3,867.3  
Cost of energy 193.6 165.9 1,102.9 755.6  
Utilities Operating Expense, Maintenance and Operations 401.1 357.4 1,225.1 1,093.5  
Taxes, Miscellaneous 74.6 65.7 238.4 210.4  
Depreciation, Depletion and Amortization 306.9 269.5 852.2 765.1  
Operating Segments          
Segment Reporting Information [Line Items]          
Consolidated Operating Income (Loss) 284.7 212.5 1,298.6 1,029.8  
Regulated Operating Revenue 1,275.5 1,079.6 4,746.5 3,877.1  
Cost of energy 193.7 165.9 1,103.0 755.6  
Utilities Operating Expense, Maintenance and Operations 427.9 380.6 1,291.6 1,161.4  
Taxes, Miscellaneous 71.1 60.8 227.1 197.3  
Segment Reporting, Other Segment Item, Amount 0.1   1.1 (0.1)  
Depreciation, Depletion and Amortization 298.0 259.8 825.1 733.1  
Operating Segments | Nonrelated Party          
Segment Reporting Information [Line Items]          
Regulated Operating Revenue 1,271.9 1,076.0 4,735.7 3,866.7  
Operating Segments | Related Party          
Segment Reporting Information [Line Items]          
Regulated Operating Revenue 3.6 3.6 10.8 10.4  
Corporate and Other          
Segment Reporting Information [Line Items]          
Consolidated Operating Income (Loss) 12.8 5.8      
Total Assets 1,300.2   1,300.2   1,195.1
Regulated Operating Revenue 151.8 145.9 441.8 425.1  
Eliminations          
Segment Reporting Information [Line Items]          
Regulated Operating Revenue (154.2) (149.2) (449.0) (434.9)  
Corporate and Other          
Segment Reporting Information [Line Items]          
Consolidated Operating Income (Loss)     21.2 8.9  
Corporate and Other | Unaffiliated          
Segment Reporting Information [Line Items]          
Revenues 1.2 0.3 3.6 0.6  
Columbia Operations | Unaffiliated          
Segment Reporting Information [Line Items]          
Revenues     2,326.7 1,864.5  
Columbia Operations | Operating Segments          
Segment Reporting Information [Line Items]          
Consolidated Operating Income (Loss) 52.1 41.2 620.1 499.8  
Total Assets 15,267.9   15,267.9   14,769.5
Regulated Operating Revenue 488.2 426.7 2,336.7 1,874.1  
Cost of energy 58.5 34.2 548.7 319.3  
Utilities Operating Expense, Maintenance and Operations 212.8 202.9 663.5 604.9  
Taxes, Miscellaneous 52.0 45.4 171.4 149.5  
Segment Reporting, Other Segment Item, Amount 0.1   0.4 0.0  
Depreciation, Depletion and Amortization 112.7 103.0 332.6 300.6  
Columbia Operations | Operating Segments | Nonrelated Party          
Segment Reporting Information [Line Items]          
Regulated Operating Revenue 484.9 423.4 2,326.7 1,864.5  
Columbia Operations | Operating Segments | Related Party          
Segment Reporting Information [Line Items]          
Regulated Operating Revenue 3.3 3.3 10.0 9.6  
NIPSCO Operations          
Segment Reporting Information [Line Items]          
Regulated Operating Revenue 787.0 652.6      
NIPSCO Operations | Unaffiliated          
Segment Reporting Information [Line Items]          
Revenues     2,409.0 2,002.2  
NIPSCO Operations | Intersegment          
Segment Reporting Information [Line Items]          
Revenues       0.8  
NIPSCO Operations | Operating Segments          
Segment Reporting Information [Line Items]          
Consolidated Operating Income (Loss) 232.6 171.3 678.5 530.0  
Total Assets 17,834.8   17,834.8   $ 15,823.5
Regulated Operating Revenue 787.3 652.9 2,409.8 2,003.0  
Cost of energy 135.2 131.7 554.3 436.3  
Utilities Operating Expense, Maintenance and Operations 215.1 177.7 628.1 556.5  
Taxes, Miscellaneous 19.1 15.4 55.7 47.8  
Segment Reporting, Other Segment Item, Amount 0.0   0.7 (0.1)  
Depreciation, Depletion and Amortization 185.3 156.8 492.5 $ 432.5  
NIPSCO Operations | Operating Segments | Nonrelated Party          
Segment Reporting Information [Line Items]          
Regulated Operating Revenue 787.0 652.6 2,409.0    
NIPSCO Operations | Operating Segments | Related Party          
Segment Reporting Information [Line Items]          
Regulated Operating Revenue $ 0.3 $ 0.3 $ 0.8    
v3.25.3
Supplemental Disclosures of Cash Flow Information (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Supplemental Cash Flow Elements [Abstract]      
Accounts Receivable, Sale $ 263.3 $ 290.0  
Increase (Decrease) in Finished Goods and Work in Process Inventories (86.2) 101.3  
Increase (Decrease) in Accounts Payable (223.5) (182.6)  
Customer Advances and Deposits 4.6 32.8  
Increase (Decrease) in Accrued Taxes Payable 7.3 (31.0)  
Debt Instrument, Increase, Accrued Interest 40.9 11.0  
Increase Decrease In Exchange Gas Receivable Payable   (161.6) $ 59.8
Increase Decrease In Other Accruals (20.4) (17.8)  
Increase Decrease In Prepayments And Other Current Assets (45.4) (61.2)  
Employee Benefits and Share-Based Compensation (26.4) (1.1)  
Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital (26.0) (85.8)  
Dividends Payable, Current $ 137.4 $ 125.3 $ 137.4
v3.25.3
Subsequent Event (Narrative) (Details) - USD ($)
$ in Millions
 9 Months Ended
Oct. 28, 2025
Sep. 30, 2025
Sep. 30, 2024
Subsequent Event [Line Items]      
Payment to renewable generation asset developer   $ 1,091.7 $ 478.8
Investment Company, Committed Capital $ 1,325.0    
Business Combination, Price of Acquisition, Expected $ 35.2    
NIPSCO Holdings II      
Subsequent Event [Line Items]      
Subsidiary, Ownership Percentage, Parent 19.90%    
Subsidiary, Ownership Percentage, Noncontrolling Owner 14.90%    
Investment Company, Committed Capital $ 175.0    
Generation Holdings II      
Subsequent Event [Line Items]      
Subsidiary, Ownership Percentage, Parent 17.50%