v3.26.3
Other Commitments And Contingencies (Narrative) (Details)
$ in Millions
 3 Months Ended 9 Months Ended
Oct. 28, 2025
USD ($)
Rate
Sep. 30, 2026
USD ($)
Rate
MW
Sep. 30, 2026
USD ($)
Rate
MW
Oct. 16, 2026
USD ($)
mMDth
Dec. 31, 2025
USD ($)
Other Commitments And Contingencies [Line Items]          
Guaranty Liabilities   $ 272.6 $ 272.6   $ 27.2
Recorded reserves to cover environmental remediation at various sites   $ 79.0 $ 79.0   82.6
Wind Power Purchase Agreement, Purchase Percentage | Rate   100.00% 100.00%    
Business Combination, Price of Acquisition, Expected $ 35.2        
Contractual Obligation   $ 58.3 $ 58.3   52.0
Long-Term Purchase Commitment, Amount   658.7      
Noncancelable Commitments - e-storage   $ 122.7 122.7    
2028 through 2030 market capacity purchase commitments     174.6    
Capacity Purchase Commitments     $ 1,100.0    
NIPSCO Holdings II          
Other Commitments And Contingencies [Line Items]          
Subsidiary, Ownership Percentage, Parent | Rate 19.90%        
Subsequent Event          
Other Commitments And Contingencies [Line Items]          
Battery Energy Storage System Energy Capacity | mMDth       2,400  
Battery Energy Storage System Power Capacity | mMDth       600  
MGP Sites          
Other Commitments And Contingencies [Line Items]          
Number of waste disposal sites identified by program   35 35    
Liability for Estimated Remediation Costs   $ 71.2 $ 71.2   75.5
us-gaap_VariableInterestEntityPrimaryBeneficiaryMemberGenCo          
Other Commitments And Contingencies [Line Items]          
Nameplate Capacity | MW   167 167    
GenCo Operations | Subsequent Event          
Other Commitments And Contingencies [Line Items]          
Contractual Obligation       $ 2,200.0  
Standby Letters of Credit          
Other Commitments And Contingencies [Line Items]          
Long-term Line of Credit   $ 98.4 $ 98.4   $ 119.0