Jointly Owned Utility Facilities - NPC (Details) $ in Millions	Dec. 31, 2020 USD ($)
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 10,443
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	5,167
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	172
Nevada Power Company [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	201
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	53
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 1
Nevada Power Company [Member] | Navajo Generating Station [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	11.00%	[1]
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 10	[1]
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	4	[1]
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 0	[1]
Nevada Power Company [Member] | ON Line deferrals
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	19.00%
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 125
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	20
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	1
Nevada Power Company [Member] | Other Transmission Facilities [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	66
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	29
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 0

[1] Includes amounts related to nuclear fuel.