Segment Information Segment Information - SPPC (Details) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) OperatingSegments TheNumberOfReportableSegments	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | OperatingSegments				8
Operating revenue		$ 5,644	$ 5,637	$ 15,148	$ 15,070
Operating income		1,450	1,523	3,328	3,366
Interest expense		(475)	(453)	(1,428)	(1,380)
Capitalized interest		23	17	56	44
Allowance for equity funds		56	30	126	75
Other, net		2	19	67	50
Income before income tax expense and equity income		847	1,423	1,944	1,904
Assets		97,913		$ 97,913		$ 92,189
Sierra Pacific Power Company [Member]
Segment Reporting Information [Line Items]
Number of reportable segments | TheNumberOfReportableSegments				2
Operating revenue		248	239	$ 661	649
Operating income		67	56	131	122
Interest expense		(12)	(12)	(36)	(33)
Capitalized interest		0	0	1	1
Allowance for equity funds		0	1	2	3
Other, net		1	3	4	8
Income before income tax expense and equity income		56	48	102	101
Assets		3,668		3,668		3,569
Sierra Pacific Power Company [Member] | Regulated electric
Segment Reporting Information [Line Items]
Regulated Operating Revenue		232	225	586	575
Operating revenue		232	225	586	575
Operating income		67	56	119	111
Assets		3,282		3,282		3,177
Sierra Pacific Power Company [Member] | Regulated natural gas
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Gas		16	14	75	74
Operating revenue		16	14	75	74
Operating income		0	$ 0	12	$ 11
Assets		304		304		314
Sierra Pacific Power Company [Member] | Regulated common assets [Member]
Segment Reporting Information [Line Items]
Assets	[1]	$ 82		$ 82		$ 78

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