Trust Investments (Fair Values And Gross Unrealized Gains And Losses For The Securities Held) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023		Sep. 30, 2023		Dec. 31, 2022
Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Trust Investments, Cost	$ 2,163		$ 2,163		$ 2,130
Gross Unrealized Gains	360		360		301
Gross Unrealized Losses	(209)		(209)		(203)
Trust Investments, Fair Value	2,314	[1]	2,314	[1]	2,228	[2]
NDT Fund Foreign Currency	2		2		2
Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Trust Investments, Cost	202		202		213
Gross Unrealized Gains	6		6		6
Gross Unrealized Losses	(41)		(41)		(36)
Trust Investments, Fair Value	167		167		183
Total Debt Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,319		1,319		1,318
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0		0		1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(178)		(178)		(163)
Debt Securities, Available-for-Sale, Fair Value	1,141		1,141		1,156
Total Debt Securities [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	191		191		199
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0		0		0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(41)		(41)		(36)
Debt Securities, Available-for-Sale, Fair Value	150		150		163
Equity Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Equity Securities, Cost	844		844		812
Equity Securities, Accumulated Gross Unrealized Gain			360		300
Equity Securities, FV-NI, Unrealized Loss			(31)		(40)
Equity Securities, Fair Value	1,173		1,173		1,072
Unrealized Gains (Losses) on Equity Securities still held	(34)		79
Equity Securities [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Unrealized Gains (Losses) on Equity Securities still held	(2)		1
Corporate Debt Obligations [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	559		559		597
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0		0		1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(61)		(61)		(69)
Debt Securities, Available-for-Sale, Fair Value	498		498		529
Corporate Debt Obligations [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	82		82		89
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0		0		0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(16)		(16)		(15)
Debt Securities, Available-for-Sale, Fair Value	66		66		74
Government Debt Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	760		760		721
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0		0		0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(117)		(117)		(94)
Debt Securities, Available-for-Sale, Fair Value	643		643		627
Government Debt Securities [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	109		109		110
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0		0		0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(25)		(25)		(21)
Debt Securities, Available-for-Sale, Fair Value	84		84		89
International Equity Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Equity Securities, Cost	372		372		336
Equity Securities, Accumulated Gross Unrealized Gain			80		68
Equity Securities, FV-NI, Unrealized Loss			(23)		(28)
Equity Securities, Fair Value	429		429		376
Domestic Equity Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Equity Securities, Cost	472		472		476
Equity Securities, Accumulated Gross Unrealized Gain			280		232
Equity Securities, FV-NI, Unrealized Loss			(8)		(12)
Equity Securities, Fair Value	744		744		696
Domestic Equity Securities [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Equity Securities, Cost	11		11		14
Equity Securities, Accumulated Gross Unrealized Gain			6		6
Equity Securities, FV-NI, Unrealized Loss			0		0
Equity Securities, Fair Value	$ 17		17		$ 20
Debt Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
After tax amount of net unrealized gains (losses) recognized in AOCI			(104)
Debt Securities [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
After tax amount of net unrealized gains (losses) recognized in AOCI			$ (30)

[1] The NDT Fund Investments table excludes cash and foreign currency of $2 million as of September 30, 2023, which is part of the NDT Fund.

[2] The NDT Fund Investments table excludes cash and foreign currency of $2 million as of December 31, 2022, which is part of the NDT Fund.