Variable Interest Entities (VIEs) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Operating Revenues	$ 9,722	$ 9,603	$ 10,076
Operation and Maintenance	3,226	3,115	3,111
Long Island ServCo [Member]
Variable Interest Entity [Line Items]
Operating Revenues	511	520	490
Operation and Maintenance	511	$ 520	$ 490
Ocean Wind JV Holdco
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	111
Ocean Wind JV Holdco | Carrying Value
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	111
Ocean Wind JV Holdco | Anticipated Spend
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 250