Derivative Instruments and Hedging Activities, Pro Forma Impact - Offsetting Collateral (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Derivative Asset [Abstract]
Gross collateral	$ 109.0	$ 46.1
Counterparties with Offsetting Positions or Collateral [Member]
Derivative Asset [Abstract]
Gross collateral	109.0	46.1
Current Assets from Risk Management Activities [Member]
Derivative Asset [Abstract]
Gross collateral	87.3	37.1
Current Assets from Risk Management Activities [Member] | Counterparties with Offsetting Positions or Collateral [Member]
Derivative Asset [Abstract]
Gross collateral	87.3	37.1
Other Long-term Assets [Member]
Derivative Asset [Abstract]
Gross collateral	21.7	9.0
Other Long-term Assets [Member] | Counterparties with Offsetting Positions or Collateral [Member]
Derivative Asset [Abstract]
Gross collateral	$ 21.7	$ 9.0