Segment Information - SPPC (Details) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) OperatingSegments TheNumberOfReportableSegments	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments | OperatingSegments										8
Revenues										$ 19,844	$ 19,787	$ 18,614
Operating income (loss)										4,150	4,072	4,522
Interest expense										1,912	1,838	1,841
Capitalized interest and allowance for borrowed funds										77	61	45
Allowance for equity funds										173	104	76
Other, net										97	(9)	(420)
Income before income tax expense and equity income										2,414	1,965	2,507
Assets		$ 100,051				$ 92,189				$ 100,051	92,189	90,208
Sierra Pacific Power Company [Member]
Segment Reporting Information [Line Items]
Number of Reportable Segments | TheNumberOfReportableSegments										2
Revenues										$ 889	855	812
Operating income (loss)		40	$ 67	$ 27	$ 37	30	$ 56	$ 19	$ 47	171	152	197
Interest expense										48	44	43
Capitalized interest and allowance for borrowed funds										1	1	2
Allowance for equity funds										3	4	3
Other, net										4	9	5
Income before income tax expense and equity income										131	122	164
Assets		3,671				3,569				3,671	3,569	3,413
Sierra Pacific Power Company [Member] | Electricity, US Regulated [Member]
Segment Reporting Information [Line Items]
Revenues										770	752	713
Operating income (loss)										150	136	175
Assets		3,319				3,177				3,319	3,177	3,103
Sierra Pacific Power Company [Member] | Natural Gas, US Regulated [Member]
Segment Reporting Information [Line Items]
Revenues										119	103	99
Operating income (loss)										21	16	22
Assets		308				314				308	314	300
Sierra Pacific Power Company [Member] | Regulated common assets [Member]
Segment Reporting Information [Line Items]
Assets	[1]	$ 44				$ 78				$ 44	$ 78	$ 10

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