Segment Information Segment Information - SPPC (Details) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) OperatingSegments TheNumberOfReportableSegments	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | OperatingSegments				8
Operating revenue		$ 4,612	$ 4,894	$ 9,139	$ 9,504
Operating income		936	959	1,855	1,878
Interest expense		(503)	(476)	(986)	(953)
Allowance for borrowed funds		19	17	36	33
Allowance for equity funds		38	38	72	70
Other, net		52	30	25	65
Income before income tax expense and equity income		1,145	610	1,652	1,097
Assets		104,417		$ 104,417		$ 100,051
Sierra Pacific Power Company [Member]
Segment Reporting Information [Line Items]
Number of reportable segments | TheNumberOfReportableSegments				2
Operating revenue		185	194	$ 417	413
Operating income		23	27	63	64
Interest expense		(14)	(12)	(28)	(24)
Allowance for borrowed funds		1	1	1	1
Allowance for equity funds		1	1	2	2
Other, net		3	1	4	3
Income before income tax expense and equity income		14	18	42	46
Assets		3,711		3,711		3,671
Sierra Pacific Power Company [Member] | Regulated electric
Segment Reporting Information [Line Items]
Regulated Operating Revenue		165	172	349	354
Operating income		20	23	53	52
Assets		3,375		3,375		3,319
Sierra Pacific Power Company [Member] | Regulated natural gas
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Gas		20	22	68	59
Operating income		3	$ 4	10	$ 12
Assets		309		309		308
Sierra Pacific Power Company [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Assets	[1]	$ 27		$ 27		$ 44

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