Income Taxes - SPPC - Summary of Operating Loss Carryforwards (Details) - Sierra Pacific Power Company [Member] $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 95
Deferred Tax Assets, Operating Loss Carryforwards	33
Deferred Tax Assets, Tax Credit Carryforwards	$ 5
Minimum [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2031
Tax Credit Carryforward, Expiration Date	Dec. 31, 2016
Maximum [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2035
Tax Credit Carryforward, Expiration Date	Dec. 31, 2035