Trust Investments (Fair Values And Gross Unrealized Gains And Losses For The Securities) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021		Dec. 31, 2020
Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Cost	$ 2,157		$ 1,990
Gross Unrealized Gains	510		523
Gross Unrealized Losses	(32)		(14)
Fair Value	2,635	[1]	2,499
Nuclear Decommissioning Trust (NDT) Fund [Member] | Domestic Equity Securities [Member]
Schedule of Trust Investments [Line Items]
Cost	491		519
Equity Securities, FV-NI, Unrealized Gain	363		305
Gross Unrealized Losses	(3)		(3)
Fair Value	851		821
Nuclear Decommissioning Trust (NDT) Fund [Member] | International Equity Securities [Member]
Schedule of Trust Investments [Line Items]
Cost	346		388
Equity Securities, FV-NI, Unrealized Gain	119		152
Gross Unrealized Losses	(15)		(9)
Fair Value	450		531
Nuclear Decommissioning Trust (NDT) Fund [Member] | Equity Securities [Member]
Schedule of Trust Investments [Line Items]
Cost	837		907
Equity Securities, FV-NI, Unrealized Gain	482		457
Gross Unrealized Losses	(18)		(12)
Fair Value	1,301		1,352
Unrealized Gains (Losses) on Equity Securities still held	130
Nuclear Decommissioning Trust (NDT) Fund [Member] | Government Obligations [Member]
Schedule of Trust Investments [Line Items]
Cost	683		555
Gross Unrealized Gains	12		27
Gross Unrealized Losses	(8)		(1)
Fair Value	687		581
Nuclear Decommissioning Trust (NDT) Fund [Member] | Corporate Debt Securities [Member]
Schedule of Trust Investments [Line Items]
Cost	637		528
Gross Unrealized Gains	16		39
Gross Unrealized Losses	(6)		(1)
Fair Value	647		566
Nuclear Decommissioning Trust (NDT) Fund [Member] | Debt Securities [Member]
Schedule of Trust Investments [Line Items]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent	8
Cost	1,320		1,083
Gross Unrealized Gains	28		66
Gross Unrealized Losses	(14)		(2)
Fair Value	1,334		1,147
Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Cost	226		238
Gross Unrealized Gains	18		28
Gross Unrealized Losses	(2)		0
Fair Value	242		266
Rabbi Trust [Member] | Domestic Equity Securities [Member]
Schedule of Trust Investments [Line Items]
Cost	14		21
Equity Securities, FV-NI, Unrealized Gain	12		10
Gross Unrealized Losses	0		0
Fair Value	26		31
Rabbi Trust [Member] | Equity Securities [Member]
Schedule of Trust Investments [Line Items]
Unrealized Gains (Losses) on Equity Securities still held	1
Rabbi Trust [Member] | Government Obligations [Member]
Schedule of Trust Investments [Line Items]
Cost	107		94
Gross Unrealized Gains	1		6
Gross Unrealized Losses	(1)		0
Fair Value	107		100
Rabbi Trust [Member] | Corporate Debt Securities [Member]
Schedule of Trust Investments [Line Items]
Cost	105		123
Gross Unrealized Gains	5		12
Gross Unrealized Losses	(1)		0
Fair Value	109		135
Rabbi Trust [Member] | Debt Securities [Member]
Schedule of Trust Investments [Line Items]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent	3
Cost	212		217
Gross Unrealized Gains	6		18
Gross Unrealized Losses	(2)		0
Fair Value	$ 216		$ 235

[1] The NDT Fund Investments table excludes foreign currency of $2 million as of December 31, 2021,         which is part of the NDT Fund.