Commitments and Contingencies - NPC - Commitments Table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Contractual Obligation [Line Items]
Contractual Obligation, Due in Next Twelve Months	$ 4,082
Contractual Obligation, Due in Second Year	2,167
Contractual Obligation, Due in Third Year	1,631
Contractual Obligation, Due in Fourth Year	1,497
Contractual Obligation, Due in Fifth Year	1,354
Contractual Obligation, Due after Fifth Year	11,311
Contractual Obligation	22,042
Operating Leases, Rent Expense	161	$ 146	$ 118
Fuel, capacity and transmission contract commitments [Member]
Contractual Obligation [Line Items]
Purchase Obligation, Due in Next Twelve Months	2,214
Purchase Obligation, Due in Second Year	1,760
Purchase Obligation, Due in Third Year	1,345
Purchase Obligation, Due in Fourth Year	1,229
Purchase Obligation, Due in Fifth Year	1,129
Purchase Obligation, Due after Fifth Year	9,494
Purchase Obligation	17,171
Maintenance, service and other contracts [Member]
Contractual Obligation [Line Items]
Purchase Obligation, Due in Next Twelve Months	181
Purchase Obligation, Due in Second Year	264
Purchase Obligation, Due in Third Year	180
Purchase Obligation, Due in Fourth Year	188
Purchase Obligation, Due in Fifth Year	156
Purchase Obligation, Due after Fifth Year	805
Purchase Obligation	1,774
Nevada Power Company [Member]
Contractual Obligation [Line Items]
Contractual Obligation, Due in Next Twelve Months	669
Contractual Obligation, Due in Second Year	622
Contractual Obligation, Due in Third Year	399
Contractual Obligation, Due in Fourth Year	395
Contractual Obligation, Due in Fifth Year	402
Contractual Obligation, Due after Fifth Year	5,366
Contractual Obligation	7,853
Rent expense for power purchase agreements meeting definition of operating lease	264	245	400
Operating Leases, Rent Expense	11	$ 10	$ 9
Nevada Power Company [Member] | Fuel, capacity and transmission contract commitments [Member]
Contractual Obligation [Line Items]
Purchase Obligation, Due in Next Twelve Months	612
Purchase Obligation, Due in Second Year	478
Purchase Obligation, Due in Third Year	330
Purchase Obligation, Due in Fourth Year	328
Purchase Obligation, Due in Fifth Year	330
Purchase Obligation, Due after Fifth Year	4,587
Purchase Obligation	6,665
Nevada Power Company [Member] | Fuel, capacity and transmission contract commitments, Not commercially operable
Contractual Obligation [Line Items]
Purchase Obligation, Due in Next Twelve Months	0
Purchase Obligation, Due in Second Year	20
Purchase Obligation, Due in Third Year	23
Purchase Obligation, Due in Fourth Year	23
Purchase Obligation, Due in Fifth Year	30
Purchase Obligation, Due after Fifth Year	603
Purchase Obligation	699
Nevada Power Company [Member] | Operating Leases, Easements, Maintenance and Service [Member]
Contractual Obligation [Line Items]
Purchase Obligation, Due in Next Twelve Months	11
Purchase Obligation, Due in Second Year	8
Purchase Obligation, Due in Third Year	8
Purchase Obligation, Due in Fourth Year	7
Purchase Obligation, Due in Fifth Year	7
Purchase Obligation, Due after Fifth Year	67
Purchase Obligation	108
Nevada Power Company [Member] | Maintenance, service and other contracts [Member]
Contractual Obligation [Line Items]
Purchase Obligation, Due in Next Twelve Months	46
Purchase Obligation, Due in Second Year	116
Purchase Obligation, Due in Third Year	38
Purchase Obligation, Due in Fourth Year	37
Purchase Obligation, Due in Fifth Year	35
Purchase Obligation, Due after Fifth Year	109
Purchase Obligation	$ 381