Trust Investments (Fair Values And Gross Unrealized Gains And Losses For The Securities Held) (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2024		Dec. 31, 2023
Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Trust Investments, Cost	$ 2,258		$ 2,219
Gross Unrealized Gains	504		428
Gross Unrealized Losses	(135)		(124)
Trust Investments, Fair Value	2,627	[1]	2,523	[2]
NDT Fund Foreign Currency	1		1
Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Trust Investments, Cost	195		200
Gross Unrealized Gains	9		8
Gross Unrealized Losses	(31)		(29)
Trust Investments, Fair Value	173		179
Total Debt Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,326		1,314
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	5		10
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(119)		(111)
Debt Securities, Available-for-Sale, Fair Value	1,212		1,213
Total Debt Securities [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	186		190
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0		0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(31)		(29)
Debt Securities, Available-for-Sale, Fair Value	155		161
Equity Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Equity Securities, Cost	932		905
Equity Securities, Accumulated Gross Unrealized Gain	499		418
Equity Securities, FV-NI, Unrealized Loss	(16)		(13)
Equity Securities, Fair Value	1,415		1,310
Unrealized Gains (Losses) on Equity Securities still held	92
Equity Securities [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Unrealized Gains (Losses) on Equity Securities still held	1
Corporate Debt Obligations [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	555		555
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	4		6
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(37)		(39)
Debt Securities, Available-for-Sale, Fair Value	522		522
Corporate Debt Obligations [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	78		80
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0		0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(10)		(10)
Debt Securities, Available-for-Sale, Fair Value	68		70
Government Debt Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	771		759
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1		4
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(82)		(72)
Debt Securities, Available-for-Sale, Fair Value	690		691
Government Debt Securities [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	108		110
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0		0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(21)		(19)
Debt Securities, Available-for-Sale, Fair Value	87		91
International Equity Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Equity Securities, Cost	418		423
Equity Securities, Accumulated Gross Unrealized Gain	137		118
Equity Securities, FV-NI, Unrealized Loss	(14)		(11)
Equity Securities, Fair Value	541		530
Domestic Equity Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Equity Securities, Cost	514		482
Equity Securities, Accumulated Gross Unrealized Gain	362		300
Equity Securities, FV-NI, Unrealized Loss	(2)		(2)
Equity Securities, Fair Value	874		780
Domestic Equity Securities [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Equity Securities, Cost	9		10
Equity Securities, Accumulated Gross Unrealized Gain	9		8
Equity Securities, FV-NI, Unrealized Loss	0		0
Equity Securities, Fair Value	18		$ 18
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	(67)
Debt Securities [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
After tax amount of net unrealized gains (losses) recognized in AOCI	$ (23)

[1] The NDT Fund Investments table excludes cash and foreign currency of $1 million as of March 31, 2024, which is part of the NDT Fund.

[2] The NDT Fund Investments table excludes cash and foreign currency of $1 million as of December 31, 2023, which is part of the NDT Fund.