Segment Information Segment Information - SPPC (Details) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) OperatingSegments TheNumberOfReportableSegments	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | OperatingSegments				8
Operating revenue		$ 4,894	$ 4,993	$ 9,504	$ 9,433
Operating income		959	972	1,878	1,843
Interest expense		(476)	(461)	(953)	(927)
Allowance for equity funds		38	24	70	45
Other, net		30	1	65	31
Income before income tax expense and equity income		610	196	1,097	481
Assets		96,142		$ 96,142		$ 92,189
Sierra Pacific Power Company [Member]
Segment Reporting Information [Line Items]
Number of reportable segments | TheNumberOfReportableSegments				2
Operating revenue		194	188	$ 413	410
Operating income		27	19	64	66
Interest expense		(12)	(11)	(24)	(21)
Allowance for Funds Used During Construction, Capitalized Interest		1	1	1	1
Allowance for equity funds		1	1	2	2
Other, net		1	3	3	5
Income before income tax expense and equity income		18	13	46	53
Assets		3,594		3,594		3,569
Sierra Pacific Power Company [Member] | Regulated electric
Segment Reporting Information [Line Items]
Regulated Operating Revenue		172	169	354	350
Operating revenue		172	169	354	350
Operating income		23	18	52	55
Assets		3,237		3,237		3,177
Sierra Pacific Power Company [Member] | Regulated natural gas
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Gas		22	19	59	60
Operating revenue		22	19	59	60
Operating income		4	$ 1	12	$ 11
Assets		316		316		314
Sierra Pacific Power Company [Member] | Regulated common assets [Member]
Segment Reporting Information [Line Items]
Assets	[1]	$ 41		$ 41		$ 78

[1] (1)Consists principally of cash and cash equivalents not included in either the regulated electric or regulated natural gas segments.