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Other Commitments And Contingencies (Narrative) (Details)
$ in Millions
 12 Months Ended
Dec. 31, 2023
USD ($)
Rate
MW
Jan. 31, 2024
Jan. 04, 2024
USD ($)
Jun. 17, 2023
Rate
Dec. 31, 2022
USD ($)
Other Commitments And Contingencies [Line Items]          
Wind power purchase agreement capacity | MW 700        
Major Rail Operators 3        
Line of Credit Facility, Amount Outstanding $ 0.0       $ 0.0
Guarantor Obligations, Current Carrying Value $ 646.1       841.6
Wind Power Purchase Agreement, Purchase Percentage | Rate 100.00%        
Accrual for Environmental Loss Contingencies, Gross $ 80.0       86.5
Other Commitment $ 250.0        
Linde Inc.          
Other Commitments And Contingencies [Line Items]          
Estimated Maximum Disgorgement Exposure     $ 48.5    
NIPSCO Holdings II          
Other Commitments And Contingencies [Line Items]          
Subsidiary, Ownership Percentage, Noncontrolling Owner   4.50%      
Subsidiary, Ownership Percentage, Parent | Rate       19.90%  
NIPSCO Holdings II | Director          
Other Commitments And Contingencies [Line Items]          
Subsidiary, Ownership Percentage, Parent | Rate 17.50%        
MGP Sites          
Other Commitments And Contingencies [Line Items]          
Number of waste disposal sites identified by program 53        
Liability for estimated remediation costs $ 73.7       81.0
Reasonably possible remediation costs variance from reserve $ 15.1        
NIPSCO          
Other Commitments And Contingencies [Line Items]          
Estimated Maximum Disgorgement Exposure     $ 7.7    
Coal Transportation | Maximum          
Other Commitments And Contingencies [Line Items]          
Long Term Purchase Commitment Expiration Year 2025        
Pipeline Service Agreements [Member] | Maximum          
Other Commitments And Contingencies [Line Items]          
Long Term Purchase Commitment Expiration Year 2038        
Pipeline Service Agreements [Member] | Minimum          
Other Commitments And Contingencies [Line Items]          
Long Term Purchase Commitment Expiration Year 2024        
IT Service Agreements [Member] | Maximum          
Other Commitments And Contingencies [Line Items]          
Long Term Purchase Commitment Expiration Year 2028        
Standby Letters of Credit          
Other Commitments And Contingencies [Line Items]          
Line of Credit Facility, Amount Outstanding $ 9.9       $ 10.2