Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss)		$ 17,841		$ 17,616
Interest Rate Derivatives, Tax		(27)	$ (53)
Gains and Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss)		(30)	(58)	(53)	$ (54)
Net current period other comprehensive income (loss)		23	(4)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		22	(5)
Gains and Losses on Cash Flow Hedges | Interest Rate Swap
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Losses reclassified from net accumulated other comprehensive loss	[1]	1	1
Defined Benefit Pension and Postretirement Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss)		(41)	(39)	(41)	(39)
Net current period other comprehensive income (loss)		0	0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		0	0
Defined Benefit Pension and Postretirement Items | Interest Rate Swap
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Losses reclassified from net accumulated other comprehensive loss	[1]	0	0
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss)		(71)	(97)	$ (94)	$ (93)
Net current period other comprehensive income (loss)		23	(4)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		22	(5)
Total | Interest Rate Swap
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Losses reclassified from net accumulated other comprehensive loss	[1]	$ 1	$ 1

[1] Included in interest charges.