Segment Information Segment Information - SPPC (Details) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) OperatingSegments TheNumberOfReportableSegments	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | OperatingSegments				8
Revenues		$ 4,554	$ 4,121	$ 8,720	$ 8,162
Cost of sales		1,049	970	2,168	2,065
Operating income		1,049	854	2,020	1,807
Interest expense		457	468	915	941
Assets		87,809		$ 87,809		$ 85,440
Sierra Pacific Power Company [Member]
Segment Reporting Information [Line Items]
Number of reportable segments | TheNumberOfReportableSegments				2
Electric Domestic Regulated Revenue		160	162	$ 319	332
Gas Domestic Regulated Revenue		17	19	51	66
Revenues		177	181	370	398
Cost of sales		61	65	117	135
Cost of Purchased Oil and Gas		6	7	22	37
Cost of Sales		67	72	139	172
Gross Margin		110	109	231	226
Utilities Operating Expense, Maintenance and Operations		40	45	81	86
Utilities Operating Expense, Depreciation and Amortization		28	29	56	58
Operating income		36	28	82	69
Interest expense		11	14	22	30
Assets		3,434		3,434		3,493
Sierra Pacific Power Company [Member] | Electric Operations [Member]
Segment Reporting Information [Line Items]
Electric Domestic Regulated Revenue		160	162	319	332
Cost of sales		61	65	117	135
Gross Margin		99	97	202	197
Utilities Operating Expense, Maintenance and Operations		36	40	72	76
Utilities Operating Expense, Depreciation and Amortization		24	25	49	50
Operating income		34	26	70	59
Interest expense		10	13	20	27
Assets		3,117		3,117		3,119
Sierra Pacific Power Company [Member] | Natural Gas Operations [Member]
Segment Reporting Information [Line Items]
Gas Domestic Regulated Revenue		17	19	51	66
Cost of Purchased Oil and Gas		6	7	22	37
Gross Margin		11	12	29	29
Utilities Operating Expense, Maintenance and Operations		4	5	9	10
Utilities Operating Expense, Depreciation and Amortization		4	4	7	8
Operating income		2	2	12	10
Interest expense		1	$ 1	2	$ 3
Assets		306		306		314
Sierra Pacific Power Company [Member] | Regulated common assets [Member]
Segment Reporting Information [Line Items]
Assets	[1]	$ 11		$ 11		$ 60

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