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Jointly Owned Utility Facilities - NPC (Details)
$ in Millions
12 Months Ended
Dec. 31, 2016
USD ($)
Jointly Owned Utility Plant Interests [Line Items]  
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service $ 9,730
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation 4,205
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress 153
Nevada Power Company [Member]  
Jointly Owned Utility Plant Interests [Line Items]  
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service 662
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation 249
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress $ 5
Nevada Power Company [Member] | Silverhawk Generating Station [Member]  
Jointly Owned Utility Plant Interests [Line Items]  
Jointly Owned Utility Plant, Proportionate Ownership Share 75.00%
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service $ 248
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation 66
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress $ 3
Nevada Power Company [Member] | Navajo Generating Station [Member]  
Jointly Owned Utility Plant Interests [Line Items]  
Jointly Owned Utility Plant, Proportionate Ownership Share 11.00%
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service $ 213
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation 145
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress $ 2
Nevada Power Company [Member] | ON Line Transmission Line [Member]  
Jointly Owned Utility Plant Interests [Line Items]  
Jointly Owned Utility Plant, Proportionate Ownership Share 24.00%
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service $ 145
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation 12
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress $ 0
Nevada Power Company [Member] | Other Transmission Facilities [Member]  
Jointly Owned Utility Plant Interests [Line Items]  
Jointly Owned Utility Plant, Proportionate Ownership Percentage Share Various
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service $ 56
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation 26
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress $ 0