Income Taxes - PAC - Component of Net Deferred Income Tax Liability (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Deferred income tax assets:
Regulatory liabilities	$ 1,349	$ 1,420
AROs	304	304
Other	686	777
Total deferred income tax assets, net	2,995	2,974
Deferred income tax liabilities:
Property-related items	(11,814)	(10,816)
Regulatory assets	(764)	(785)
Other	(478)	(327)
Total deferred income tax liabilities	(15,933)	(14,749)
Net deferred income tax liability	(12,938)	(11,775)
PAC
Deferred income tax assets:
Regulatory liabilities	682	700
Employee benefits	68	93
State carryforwards	73	73
Loss contingencies	63	63
AROs	73	65
Other	73	83
Total deferred income tax assets, net	1,032	1,077
Deferred income tax liabilities:
Property-related items	(3,468)	(3,311)
Regulatory assets	(332)	(343)
Other	(79)	(50)
Total deferred income tax liabilities	(3,879)	(3,704)
Net deferred income tax liability	$ (2,847)	$ (2,627)