Derivative Instruments and Hedging Activities, Pro Forma Impact - Offsetting Collateral (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Derivative Asset [Abstract]
Gross collateral	$ 19.2	$ 8.1
Counterparties with Offsetting Positions or Collateral [Member]
Derivative Asset [Abstract]
Gross collateral	19.2	8.1
Current Assets from Risk Management Activities [Member]
Derivative Asset [Abstract]
Gross collateral	3.7	5.0
Current Assets from Risk Management Activities [Member] | Counterparties with Offsetting Positions or Collateral [Member]
Derivative Asset [Abstract]
Gross collateral	3.7	5.0
Long-Term Assets from Risk Management Activities [Member]
Derivative Asset [Abstract]
Gross collateral	15.5	3.1
Long-Term Assets from Risk Management Activities [Member] | Counterparties with Offsetting Positions or Collateral [Member]
Derivative Asset [Abstract]
Gross collateral	$ 15.5	$ 3.1