Trust Investments (Value Of Securities That Have Been In An Unrealized Loss Position For Less Than And Greater Than 12 Months) (Detail) - USD ($) $ in Millions		Mar. 31, 2024	Dec. 31, 2023
Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		$ 284	$ 188
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		(11)	(6)
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer		752	793
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer,		(124)	(118)
Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		11	6
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		0	0
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer		137	143
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer,		(31)	(29)
Equity Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		83	79
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		(9)	(5)
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer		23	32
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer,		(7)	(8)
Total Debt Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		201	109
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		(2)	(1)
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer		729	761
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer,		(117)	(110)
Total Debt Securities [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		11	6
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		0	0
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer		137	143
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer,		(31)	(29)
Domestic Equity Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		22	44
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		(1)	(1)
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer		5	4
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer,		(1)	0
International Equity Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		61	35
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		(8)	(4)
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer		18	28
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer,		(6)	(8)
Government Debt Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		153	90
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		(2)	(1)
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer		429	432
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer,		(80)	(71)
Government Debt Securities [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		6	3
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		0	0
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer		80	83
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer,		(21)	(19)
Corporate Debt Obligations [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		48	19
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		0	0
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer		300	329
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer,		(37)	(39)
Corporate Debt Obligations [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	[1]	5	3
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	[1]	0	0
Fair Value of Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	[1]	57	60
Gross Unrealized Losses on Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer,	[1]	$ (10)	$ (10)

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