Commitments and Contingencies - NPC - Legal (Details) - Nevada Power Company [Member]	1 Months Ended		12 Months Ended
	Jun. 30, 2016 MW	Feb. 29, 2016 MW	Dec. 31, 2016 MW	Dec. 31, 2015 power_purchase_agreements MW	Dec. 31, 2014 MW
Loss Contingencies [Line Items]
Number of Approved Renewable Power Purchase Agreements | power_purchase_agreements				2
812 Megawatts of Coal Energy [Member]
Loss Contingencies [Line Items]
Coal-Fired Power Plant Capacity			812
130 Megawatts of Natural Gas Energy [Member]
Loss Contingencies [Line Items]
New Generation Capacity			130
272 Megawatts of Renewable Energy [Member]
Loss Contingencies [Line Items]
New Generation Capacity					272
210 Megawatts of Renewable Energy [Member]
Loss Contingencies [Line Items]
New Generation Capacity					210
15 Megawatts of Solar Renewable Energy [Member]
Loss Contingencies [Line Items]
New Generation Capacity				15
100 Megawatts of Renewable Energy [Member]
Loss Contingencies [Line Items]
New Generation Capacity	100			100
35 Megawatts of Renewable Energy [Member]
Loss Contingencies [Line Items]
New Generation Capacity		35