Fair Value of Financial Assets and Liabilities - Consideration of Credit Risk Concentrations (Details) - Credit Concentration Risk $ in Millions	Mar. 31, 2023 USD ($) Counterparty
Derivative [Line Items]
Significant counterparties	10
Municipal or cooperative electric entities or other utilities
Derivative [Line Items]
Significant counterparties	9
External credit rating, investment grade
Derivative [Line Items]
Significant counterparties	4
Credit exposure | $	$ 10
Credit exposure, percentage	31.00%
Internal investment grade
Derivative [Line Items]
Significant counterparties	5
Credit exposure | $	$ 23
Credit exposure, percentage	69.00%
External Credit Rating, Non Investment Grade [Member]
Derivative [Line Items]
Significant counterparties	1
Credit exposure, percentage	1.00%