Cash and Cash Equivalents and Restricted Cash and Cash Equivalents Supplemental Cash Flow Disclosure - NPC (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	$ 2,071	$ 1,040
Restricted cash and cash equivalents	217	212
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	2,304	1,268	$ 1,857	$ 883
Nevada Power Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	121	15
Restricted cash and cash equivalents	12	10
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 133	$ 25	$ 62	$ 121