Cash and Cash Equivalents and Restricted Cash and Cash Equivalents Supplemental Cash Flow Disclosure - SPPC (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	$ 1,769	$ 1,040
Restricted cash and cash equivalents	309	212
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	2,096	1,268	$ 1,406	$ 883
Sierra Pacific Power Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	22	27
Restricted cash and cash equivalents	4	5
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 26	$ 32	$ 68	$ 76