Supplemental Cash Flow Disclosures - NPC (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	$ 1,290	$ 1,040
Restricted cash and cash equivalents	140	212
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	1,445	1,268	$ 883	$ 1,283
Interest paid, net of amounts capitalized	1,855	1,723	1,713
Accrued capital expenditures	801	888	823
Nevada Power Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	25	15
Restricted cash and cash equivalents	11	10
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	36	25	121	$ 66
Interest paid, net of amounts capitalized	115	126	166
Income taxes paid	50	113	117
Accrued capital expenditures	$ 32	$ 49	$ 34