Property, Plant and Equipment, Net - SPPC (Details) - Sierra Pacific Power Company [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Net	$ 2,766	$ 2,640
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	2.90%	3.00%	3.00%
Asset Impairment Charges		$ 12	$ 4
Asset Impairment Charges, 2014 PUCN General Rate Case		8
Electricity Generation Plant, Non-Nuclear [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation or Processing	$ 1,134	1,036
Public Utilities, Property, Plant and Equipment, Distribution	1,382	1,321
Public Utilities, Property, Plant and Equipment, Transmission	739	719
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	$ 139	$ 123
Electricity Generation Plant, Non-Nuclear [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation, Useful Life	40 years	40 years
Public Utilities, Property, Plant and Equipment, Distribution, Useful Life	20 years	20 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	5 years	5 years
Public Utilities, Property, Plant and Equipment, Transmission, Useful Life	50 years	50 years
Electricity Generation Plant, Non-Nuclear [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation, Useful Life	125 years	125 years
Public Utilities, Property, Plant and Equipment, Distribution, Useful Life	70 years	70 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	65 years	65 years
Public Utilities, Property, Plant and Equipment, Transmission, Useful Life	70 years	70 years
Natural Gas Processing Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Distribution	$ 374	$ 366
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	$ 13	$ 13
Natural Gas Processing Plant [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Distribution, Useful Life	40 years	40 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	8 years	8 years
Natural Gas Processing Plant [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Distribution, Useful Life	70 years	70 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	10 years	10 years
Common Facilities [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Common	$ 265	$ 234
Public Utilities, Property, Plant and Equipment, Plant in Service, Excluding Construction Work In Progress	4,046	3,812
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation	(1,368)	(1,300)
Public Utilities, Property, Plant and Equipment, Net, Excluding Construction Work In Progress	2,678	2,512
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	88	128
Public Utilities, Property, Plant and Equipment, Net	$ 2,766	$ 2,640
Common Facilities [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Common, Useful Life	5 years	5 years
Common Facilities [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Common, Useful Life	65 years	65 years