Income Taxes - NPC - Components of Net Deferred Income Tax Liability (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred Tax Assets and Liabilities [Line Items]
Regulatory liabilities	$ 1,610	$ 1,674
Other	590	527
Total deferred income tax assets	3,081	3,029
Property-related items	(10,439)	(10,185)
Regulatory assets	(631)	(656)
Other	(384)	(222)
Total deferred income tax liabilities	(12,591)	(11,939)
Net deferred income tax liability	(9,653)	(9,047)
Nevada Power Company [Member]
Deferred Tax Assets and Liabilities [Line Items]
Regulatory liabilities	211	209
Deferred Tax Assets, Tax Deferred Expense, Leases	99	97
Employee benefits	14	15
Deferred Tax Assets, Customer Advances	19	18
Other	9	9
Total deferred income tax assets	352	348
Property-related items	(797)	(799)
Regulatory assets	(166)	(196)
Deferred Tax Liabilities, Tax Deferred Expense, Leases	(95)	(94)
Other	(8)	(8)
Total deferred income tax liabilities	(1,066)	(1,097)
Net deferred income tax liability	$ (714)	$ (749)