Financial Risk Management Activities (Schedule Of Gross Volume, On Absolute Basis For Derivative Contracts) (Detail) $ / mwh in Millions, $ / DTH in Millions	12 Months Ended
	Dec. 31, 2021 $ / mwh $ / DTH	Dec. 31, 2020 $ / mwh $ / DTH
Natural Gas Dth [Member]
Derivative [Line Items]
Gross volume of derivative on absolute value basis | $ / DTH	(47)	(321)
Electricity MWh [Member]
Derivative [Line Items]
Underlying, Derivative Volume	(76)	(66)
FTRs MWh [Member]
Derivative [Line Items]
Gross volume of derivative on absolute value basis	(27)	(20)