Cash and Cash Equivalents and Restricted Cash and Cash Equivalents Supplemental Cash Flow Disclosure - NPC (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	$ 1,276	$ 1,290
Restricted cash and cash equivalents	117	140
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	1,406	1,445	$ 2,304	$ 1,268
Nevada Power Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	92	25
Restricted cash and cash equivalents	12	11
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 104	$ 36	$ 133	$ 25