Cash and Cash Equivalents and Restricted Cash and Cash Equivalents Supplemental Cash Flow Disclosure - SPPC (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	$ 1,815	$ 1,040
Restricted cash and cash equivalents	237	212
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	2,070	1,268	$ 1,506	$ 883
Sierra Pacific Power Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	12	27
Restricted cash and cash equivalents	5	5
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 17	$ 32	$ 33	$ 76