Commitments and Contingencies Commitments and Contingencies - NPC (Details) - Nevada Power Company [Member] - Fuel, capacity and transmission contract commitments [Member] - Subsequent Event [Member] $ in Millions	Oct. 01, 2019 USD ($)
ContractualObligationFiscalYearMaturityScheduleTable [Line Items]
Purchase Obligation, Future Minimum Payments, Remainder of Fiscal Year, Terminated	$ 60
Purchase Obligation, Due in Second Year, Terminated	60
Purchase Obligation, Due in Third Year, Terminated	60
Purchase Obligation, Due in Fourth Year, Terminated	60
Purchase Obligation, Due in Fifth Year, Terminated	60
Purchase Obligation, Due after Fifth Year, Terminated	$ 1,145