Income Taxes - Components of Net Deferred Income Tax Liability (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred income tax assets: [Abstract]
Federal, state and foreign carryforwards	$ 575	$ 596
Regulatory liabilities	1,610	1,674
AROs	306	232
Other	590	527
Total deferred income tax assets	3,081	3,029
Valuation allowances	(143)	(137)
Total deferred income tax assets, net	2,938	2,892
Deferred income tax liabilities: [ Abstract]
Property-related items	(10,439)	(10,185)
Regulatory assets	(631)	(656)
Investments	(1,137)	(876)
Other	(384)	(222)
Total deferred income tax liabilities	(12,591)	(11,939)
Net deferred income tax liability	$ (9,653)	$ (9,047)