Commitments and Contingencies - SPPC - 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
Sierra Pacific Power Company [Member]
Contractual Obligation [Line Items]
Contractual Obligation, Due in Next Twelve Months	218
Contractual Obligation, Due in Second Year	167
Contractual Obligation, Due in Third Year	116
Contractual Obligation, Due in Fourth Year	96
Contractual Obligation, Due in Fifth Year	83
Contractual Obligation, Due after Fifth Year	531
Contractual Obligation	1,211
Rent expense for power purchase agreements meeting definition of operating lease	65	68	63
Operating Leases, Rent Expense	7	$ 6	$ 5
Sierra Pacific Power Company [Member] | Fuel, capacity and transmission contract commitments [Member]
Contractual Obligation [Line Items]
Purchase Obligation, Due in Next Twelve Months	207
Purchase Obligation, Due in Second Year	159
Purchase Obligation, Due in Third Year	109
Purchase Obligation, Due in Fourth Year	88
Purchase Obligation, Due in Fifth Year	75
Purchase Obligation, Due after Fifth Year	444
Purchase Obligation	1,082
Sierra Pacific Power Company [Member] | Operating Leases, Easements, Maintenance and Service [Member]
Contractual Obligation [Line Items]
Purchase Obligation, Due in Next Twelve Months	6
Purchase Obligation, Due in Second Year	4
Purchase Obligation, Due in Third Year	3
Purchase Obligation, Due in Fourth Year	3
Purchase Obligation, Due in Fifth Year	3
Purchase Obligation, Due after Fifth Year	65
Purchase Obligation	84
Sierra Pacific Power Company [Member] | Maintenance, service and other contracts [Member]
Contractual Obligation [Line Items]
Purchase Obligation, Due in Next Twelve Months	5
Purchase Obligation, Due in Second Year	4
Purchase Obligation, Due in Third Year	4
Purchase Obligation, Due in Fourth Year	5
Purchase Obligation, Due in Fifth Year	5
Purchase Obligation, Due after Fifth Year	22
Purchase Obligation	$ 45