Commitments and Contingencies - SPPC - Commitments Table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Contractual Obligation [Line Items]
Contractual Obligation, Due in Next Twelve Months	$ 3,666
Contractual Obligation, Due in Second Year	1,997
Contractual Obligation, Due in Third Year	1,768
Contractual Obligation, Due in Fourth Year	1,482
Contractual Obligation, Due in Fifth Year	1,264
Contractual Obligation, Due after Fifth Year	11,865
Contractual Obligation	22,042
Operating Leases, Rent Expense	156	$ 161	$ 146
Fuel, capacity and transmission contract commitments [Member]
Contractual Obligation [Line Items]
Purchase Obligation, Due in Next Twelve Months	2,370
Purchase Obligation, Due in Second Year	1,606
Purchase Obligation, Due in Third Year	1,389
Purchase Obligation, Due in Fourth Year	1,208
Purchase Obligation, Due in Fifth Year	1,010
Purchase Obligation, Due after Fifth Year	10,053
Purchase Obligation	17,636
Maintenance, service and other contracts [Member]
Contractual Obligation [Line Items]
Purchase Obligation, Due in Next Twelve Months	303
Purchase Obligation, Due in Second Year	220
Purchase Obligation, Due in Third Year	212
Purchase Obligation, Due in Fourth Year	186
Purchase Obligation, Due in Fifth Year	180
Purchase Obligation, Due after Fifth Year	723
Purchase Obligation	1,824
Sierra Pacific Power Company [Member]
Contractual Obligation [Line Items]
Contractual Obligation, Due in Next Twelve Months	251
Contractual Obligation, Due in Second Year	175
Contractual Obligation, Due in Third Year	120
Contractual Obligation, Due in Fourth Year	91
Contractual Obligation, Due in Fifth Year	82
Contractual Obligation, Due after Fifth Year	653
Contractual Obligation	1,372
Rent expense for power purchase agreements meeting definition of operating lease	69	65	68
Operating Leases, Rent Expense	6	$ 7	$ 6
Sierra Pacific Power Company [Member] | Fuel, capacity and transmission contract commitments [Member]
Contractual Obligation [Line Items]
Purchase Obligation, Due in Next Twelve Months	238
Purchase Obligation, Due in Second Year	156
Purchase Obligation, Due in Third Year	103
Purchase Obligation, Due in Fourth Year	71
Purchase Obligation, Due in Fifth Year	62
Purchase Obligation, Due after Fifth Year	375
Purchase Obligation	1,005
Sierra Pacific Power Company [Member] | Operating Leases, Easements, Maintenance and Service [Member]
Contractual Obligation [Line Items]
Purchase Obligation, Due in Next Twelve Months	4
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	46
Purchase Obligation	63
Sierra Pacific Power Company [Member] | Maintenance, service and other contracts [Member]
Contractual Obligation [Line Items]
Purchase Obligation, Due in Next Twelve Months	4
Purchase Obligation, Due in Second Year	5
Purchase Obligation, Due in Third Year	4
Purchase Obligation, Due in Fourth Year	6
Purchase Obligation, Due in Fifth Year	6
Purchase Obligation, Due after Fifth Year	17
Purchase Obligation	$ 42