Variable Interest Entities (VIEs) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Variable Interest Entity [Line Items]
Operating Revenues	$ 2,313	$ 2,889
Operation and Maintenance	794	778
Long Island ServCo [Member]
Variable Interest Entity [Line Items]
Operating Revenues	123	123
Operation and Maintenance	123	$ 123
Ocean Wind JV Holdco
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	124		$ 111
Ocean Wind JV Holdco | Anticipated Spend
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 250