Derivative Financial Instruments (Schedule of Volume of Derivative Activity) (Detail) MWh in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($) MWh
Interest Rate Swap Current [Member]
Derivative [Line Items]
Interest rate(1) (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(1) (in millions) | $	$ 71
Interest Rate Swap Noncurrent [Member] | Electricity [Member]
Derivative [Line Items]
Fixed price | MWh	22