Income Taxes - SPPC - Summary of Operating Loss Carryforwards (Details) - Sierra Pacific Power Company [Member] $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 55
Deferred Tax Assets, Operating Loss Carryforwards	19
Deferred Tax Assets, Tax Credit Carryforwards	$ 6
Minimum [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2031
Tax Credit Carryforward, Expiration Date	Dec. 31, 2021
Maximum [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2033
Tax Credit Carryforward, Expiration Date	Dec. 31, 2032