Segment Information Segment Information - SPPC (Details) $ in Millions		3 Months Ended
		Mar. 31, 2021 USD ($) OperatingSegments TheNumberOfReportableSegments	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | OperatingSegments		8
Operating revenue		$ 6,081	$ 4,527
Operating income		1,333	919
Interest expense		(530)	(483)
Allowance for equity funds		26	34
Other, net		8	(27)
Income before income tax expense and equity income		(246)	507
Assets		$ 127,522		$ 127,316
Sierra Pacific Power Company [Member]
Segment Reporting Information [Line Items]
Number of reportable segments | TheNumberOfReportableSegments		2
Operating revenue		$ 220	232
Operating income		39	40
Interest expense		(14)	(14)
Allowance for equity funds		1	1
Other, net		6	1
Income before income tax expense and equity income		32	28
Assets		3,963		3,919
Sierra Pacific Power Company [Member] | Electricity Us Regulated Member
Segment Reporting Information [Line Items]
Regulated Operating Revenue		181	184
Operating income		31	33
Assets		3,589		3,540
Sierra Pacific Power Company [Member] | Natural Gas US Regulated Member
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Gas		39	48
Operating income		8	$ 7
Assets		348		342
Sierra Pacific Power Company [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Assets	[1]	$ 26		$ 37

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