Property, Plant and Equipment, Net - NPC (Details) - Nevada Power Company [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Net, Excluding Construction Work In Progress	$ 6,843	$ 6,883
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	153	120
Public Utilities, Property, Plant and Equipment, Net	$ 6,996	$ 7,003
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	3.00%	3.30%	3.30%
Asset Impairment Charges		$ 29	$ 31
Asset Impairment Charges, 2014 PUCN General Rate Case		19
Regulated Operation [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation or Processing	$ 4,212	4,034
Public Utilities, Property, Plant and Equipment, Distribution	3,118	3,018
Public Utilities, Property, Plant and Equipment, Transmission	1,788	1,757
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	694	669
Public Utilities, Property, Plant and Equipment, Plant in Service, Excluding Construction Work In Progress	9,812	9,478
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation	2,971	2,599
Public Utilities, Property, Plant and Equipment, Net, Excluding Construction Work In Progress	6,841	6,879
Nonregulated Operation [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Net, Excluding Construction Work In Progress	$ 2	$ 4
Minimum [Member] | Regulated Operation [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation, Useful Life	25 years	25 years
Public Utilities, Property, Plant and Equipment, Distribution, Useful Life	20 years	20 years
Public Utilities, Property, Plant and Equipment, Transmission, Useful Life	45 years	45 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	5 years	5 years
Minimum [Member] | Nonregulated Operation [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	5 years	5 years
Maximum [Member] | Regulated Operation [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation, Useful Life	80 years	80 years
Public Utilities, Property, Plant and Equipment, Distribution, Useful Life	65 years	65 years
Public Utilities, Property, Plant and Equipment, Transmission, Useful Life	65 years	65 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	65 years	65 years
Maximum [Member] | Nonregulated Operation [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	65 years	65 years