Derivative Instruments and Hedging Activities, Pro Forma Impact - Offsetting Collateral (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Derivative Asset [Abstract]
Gross collateral	$ 9.1	$ 8.1
Counterparties with Offsetting Positions or Collateral [Member]
Derivative Asset [Abstract]
Gross collateral	9.1	8.1
Current Assets from Risk Management Activities [Member]
Derivative Asset [Abstract]
Gross collateral	(4.7)	5.0
Current Assets from Risk Management Activities [Member] | Counterparties with Offsetting Positions or Collateral [Member]
Derivative Asset [Abstract]
Gross collateral	(4.7)	5.0
Long-Term Assets from Risk Management Activities [Member]
Derivative Asset [Abstract]
Gross collateral	13.8	3.1
Long-Term Assets from Risk Management Activities [Member] | Counterparties with Offsetting Positions or Collateral [Member]
Derivative Asset [Abstract]
Gross collateral	$ 13.8	$ 3.1