Segment Information Segment Information - SPPC (Details) $ in Millions		3 Months Ended
		Mar. 31, 2020 USD ($) OperatingSegments TheNumberOfReportableSegments	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | OperatingSegments		8
Operating revenue		$ 4,527	$ 4,610
Operating income		919	919
Interest expense		(483)	(477)
Allowance for equity funds		34	32
Other, net		(27)	35
Income before income tax expense and equity income		507	487
Assets		$ 100,806		$ 100,051
Sierra Pacific Power Company [Member]
Segment Reporting Information [Line Items]
Number of reportable segments | TheNumberOfReportableSegments		2
Operating revenue		$ 232	219
Operating income		40	37
Interest expense		(14)	(12)
Allowance for equity funds		1	1
Other, net		1	2
Income before income tax expense and equity income		28	28
Assets		3,686		3,671
Sierra Pacific Power Company [Member] | Regulated electric
Segment Reporting Information [Line Items]
Regulated Operating Revenue		184	182
Operating income		33	29
Assets		3,332		3,319
Sierra Pacific Power Company [Member] | Regulated natural gas
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Gas		48	37
Operating income		7	$ 8
Assets		314		308
Sierra Pacific Power Company [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Assets	[1]	$ 40		$ 44

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