Segment Information Segment Information - SPPC (Details) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) OperatingSegments TheNumberOfReportableSegments	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | OperatingSegments				8
Operating revenue		$ 6,193	$ 5,644	$ 15,332	$ 15,148
Operating income		1,547	1,450	3,402	3,328
Interest expense		(504)	(475)	(1,490)	(1,428)
Allowance for borrowed funds		24	23	60	56
Allowance for equity funds		50	56	122	126
Other, net		36	2	61	67
Income before income tax expense and equity income		2,967	847	4,619	1,944
Assets		109,186		$ 109,186		$ 100,051
Sierra Pacific Power Company [Member]
Segment Reporting Information [Line Items]
Number of reportable segments | TheNumberOfReportableSegments				2
Operating revenue		235	248	$ 652	661
Operating income		68	67	131	131
Interest expense		(14)	(12)	(42)	(36)
Allowance for borrowed funds		0	0	1	1
Allowance for equity funds		1	0	3	2
Other, net		3	1	7	4
Income before income tax expense and equity income		58	56	100	102
Assets		3,869		3,869		3,671
Sierra Pacific Power Company [Member] | Regulated electric
Segment Reporting Information [Line Items]
Regulated Operating Revenue		220	232	569	586
Operating income		66	67	119	119
Assets		3,515		3,515		3,319
Sierra Pacific Power Company [Member] | Regulated natural gas
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Gas		15	16	83	75
Operating income		2	$ 0	12	$ 12
Assets		318		318		308
Sierra Pacific Power Company [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Assets	[1]	$ 36		$ 36		$ 44

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