Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021		Dec. 31, 2020		Dec. 31, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive loss at Jan. 1	$ 6,769
Accumulated other comprehensive (loss) income at end of period	7,573		$ 6,769
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	0		0		$ 0
Gains and Losses on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive loss at Jan. 1	(19)		(20)
Net current period other comprehensive income	2		1
Accumulated other comprehensive (loss) income at end of period	(17)		(19)		(20)
Gains and Losses on Cash Flow Hedges | Interest Rate Swap [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Interest rate derivatives, net of tax of $—	(2)	[1]	(1)	[2]
Defined Benefit Pension and Postretirement Items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive loss at Jan. 1	(3)		(3)
Net current period other comprehensive income	0		0
Accumulated other comprehensive (loss) income at end of period	(3)		(3)		(3)
Defined Benefit Pension and Postretirement Items | Interest Rate Swap [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Interest rate derivatives, net of tax of $—	0		0
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive loss at Jan. 1	(22)		(23)
Net current period other comprehensive income	2		1
Accumulated other comprehensive (loss) income at end of period	(20)		(22)		$ (23)
Total | Interest Rate Swap [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Interest rate derivatives, net of tax of $—	$ (2)		$ (1)

[1] Included in interest charges.

[2] Included in interest charges.