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Asset Retirement Obligations (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Beginning Balance $ 96.2 $ 88.9
Liabilities Incurred 0.2 6.7
Liabilities Settled 0.0 0.0
Accretion 4.1 3.5
Revisions to Prior Estimates 0.2 (2.9)
Ending Balance 100.7 96.2
Electric Utilities    
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Beginning Balance 28.7 27.6
Liabilities Incurred 0.0 0.0
Liabilities Settled 0.0 0.0
Accretion 1.1 1.2
Revisions to Prior Estimates 0.2 (0.1)
Ending Balance 30.0 28.7
Gas Utilities    
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Beginning Balance [1] 67.5 61.3
Liabilities Incurred 0.2 6.7 [1]
Liabilities Settled 0.0 0.0 [1]
Accretion 3.0 2.3 [1]
Revisions to Prior Estimates 0.0 (2.8) [1]
Ending Balance $ 70.7 $ 67.5 [1]
[1] The Revisions to Prior Estimates were primarily driven by changes in estimates associated with natural gas wells and compressor stations.