Property, Plant and Equipment, Net Property, Plant and Equipment, Net - NPC(Details) - Nevada Power Company [Member] - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Apr. 30, 2017
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Net, Excluding Construction Work In Progress	$ 6,743	$ 6,883
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	91	114
Public Utilities, Property, Plant and Equipment, Net	6,834	6,997
130 Megawatts of Natural Gas Energy [Member] | Subsequent Event [Member]
Property, Plant and Equipment [Line Items]
Ownership Percentage Acquired			25.00%
Business Acquisition, Transaction Costs			$ 77
Regulated assets [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation or Processing	3,583	4,271
Public Utilities, Property, Plant and Equipment, Distribution	3,248	3,231
Public Utilities, Property, Plant and Equipment, Transmission	1,860	1,846
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	764	738
Public Utilities, Property, Plant and Equipment, Plant in Service, Excluding Construction Work In Progress	9,455	10,086
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation	2,715	3,205
Public Utilities, Property, Plant and Equipment, Net, Excluding Construction Work In Progress	$ 6,740	$ 6,881
Regulated assets [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation, Useful Life	30 years	30 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
Regulated assets [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation, Useful Life	55 years	55 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
Unregulated operation [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Net, Excluding Construction Work In Progress	$ 3	$ 2
Unregulated operation [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	45 years	45 years
Unregulated operation [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	45 years	45 years