Long-Term PPAs - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) MW
Long Term Contract For Purchase Of Electric Power [Line Items]
Purchased power	$ 106	$ 83	$ 49
Power Purchase Agreements [Member] | Variable Interest Entity Not Primary Beneficiary [Member]
Long Term Contract For Purchase Of Electric Power [Line Items]
Purchased power	$ 46	$ 36	$ 25
Maximum [Member]
Long Term Contract For Purchase Of Electric Power [Line Items]
PPAs range | MW			515