Derivative Financial Instruments (Schedule of Volume of Derivative Activity) (Detail) MWh in Millions, $ in Millions	6 Months Ended
	Jun. 30, 2022 USD ($) MWh
Interest Rate Swap Current [Member]
Derivative [Line Items]
Interest rate (in millions) | $	$ 0
Interest Rate Swap Current [Member] | Electricity [Member]
Derivative [Line Items]
Fixed price | MWh	2
Interest Rate Swap Noncurrent [Member]
Derivative [Line Items]
Interest rate (in millions) | $	$ 71
Interest Rate Swap Noncurrent [Member] | Electricity [Member]
Derivative [Line Items]
Fixed price | MWh	25