Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022	Dec. 31, 2021
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss)		$ 17,309		$ 17,309			$ 16,675
Interest Rate Derivatives, Tax		40	$ 44	(101)	$ (80)
Gains and Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss)		(40)	(56)	(40)	(56)	$ (44)	(54)	$ (57)	$ (75)
Losses reclassified from net accumulated other comprehensive loss	[1]	0	0	0	0
Net current period other comprehensive income (loss)		4	1	14	19
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		3	0	11	15
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	[2]	1	1	3	4
Defined Benefit Pension and Postretirement Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss)		(38)	(35)	(38)	(35)	(38)	(39)	(46)	(48)
Losses reclassified from net accumulated other comprehensive loss	[1]	0	1	1	2
Net current period other comprehensive income (loss)		0	11	1	13
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		0	10	0	11
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	[2]	0	0	0	0
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss)		(78)	(91)	(78)	(91)	$ (82)	$ (93)	$ (103)	$ (123)
Losses reclassified from net accumulated other comprehensive loss	[1]	0	1	1	2
Net current period other comprehensive income (loss)		4	12	15	32
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		3	10	11	26
Total | Interest Rate Swap
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Losses reclassified from net accumulated other comprehensive loss	[2]	$ 1	$ 1	$ 3	$ 4

[1] Included in the computation of net periodic pension and postretirement benefit costs.

[2] Included in interest charges.