Segment Information - SPPC (Details) $ in Millions		12 Months Ended
		Dec. 31, 2016 USD ($) OperatingSegments TheNumberOfReportableSegments	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments | OperatingSegments		8
Revenues		$ 17,422	$ 17,880	$ 17,326
Cost of sales		4,315	5,079	5,732
Operating income (loss)		4,251	4,328	4,046
Income tax expense		403	450	589
Payments to Acquire Property, Plant, and Equipment		5,090	5,875	6,555
Assets		$ 85,440	83,618	81,816
Sierra Pacific Power Company [Member]
Segment Reporting Information [Line Items]
Number of Reportable Segments | TheNumberOfReportableSegments		2
Electric Domestic Regulated Revenue		$ 702	810	779
Gas Domestic Regulated Revenue		110	137	125
Revenues		812	947	904
Cost of sales		265	374	361
Cost of Purchased Oil and Gas		55	84	76
Cost of Sales		320	458	437
Gross Margin		492	489	467
Operations and maintenance		170	167	162
Utilities Operating Expense, Depreciation and Amortization		118	113	105
Operating income (loss)		180	184	178
Interest expense, net of borrowed funds		54	61	61
Income tax expense		49	47	47
Payments to Acquire Property, Plant, and Equipment		194	252	186
Assets		3,493	3,487	3,336
Sierra Pacific Power Company [Member] | Electric Operations [Member]
Segment Reporting Information [Line Items]
Electric Domestic Regulated Revenue		702	810	779
Cost of sales		265	374	361
Electric Domestic Regulated Gross Margin		437	436	418
Electricity, Utilities Operating Expense, Maintenance and Operations		153	149	143
Utilities Operating Expense, Depreciation and Amortization		101	96	90
Operating income (loss)		161	168	165
Electric, Interest Expense, net of allowance for borrowed funds		49	56	57
Income tax expense		44	43	43
Payments to Acquire Property, Plant, and Equipment		176	229	168
Assets		3,119	3,060	2,984
Sierra Pacific Power Company [Member] | Natural Gas Operations [Member]
Segment Reporting Information [Line Items]
Gas Domestic Regulated Revenue		110	137	125
Cost of Purchased Oil and Gas		55	84	76
Gas Domestic Regulated Gross Margin		55	53	49
Gas, Utilities Operating Expense, Maintenance and Operations		17	18	19
Utilities Operating Expense, Depreciation and Amortization		17	17	15
Operating income (loss)		19	16	13
Gas, Interest Expense, net of allowance for borrowed funds		5	5	4
Income tax expense		5	4	4
Payments to Acquire Property, Plant, and Equipment		18	23	18
Assets		314	316	322
Sierra Pacific Power Company [Member] | Regulated common assets [Member]
Segment Reporting Information [Line Items]
Assets	[1]	$ 60	$ 111	$ 30

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