Regulatory Matters - SPPC - Regulatory Liabilities - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 3,120	$ 3,033
Regulatory liabilities		187	402
Regulatory liabilities		2,933	2,631
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[1]	2,242	2,167
Regulatory liabilities other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		327	301
Sierra Pacific Power Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		290	308
Regulatory liabilities		69	78
Regulatory liabilities		$ 221	230
Sierra Pacific Power Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		39 years
Regulatory Liabilities	[2]	$ 205	208
Sierra Pacific Power Company [Member] | Deferred Excess Energy Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		1 year
Regulatory Liabilities		$ 64	66
Sierra Pacific Power Company [Member] | Renewable Energy Program [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		1 year
Regulatory Liabilities		$ 0	8
Sierra Pacific Power Company [Member] | Regulatory liabilities other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 21	$ 26

[1] Amounts represent estimated costs, as accrued through depreciation rates and exclusive of ARO liabilities, of removing regulated property, plant and equipment in accordance with accepted regulatory practices. Amounts are deducted from rate base or otherwise accrue a carrying cost.

[2] Amounts represent estimated costs, as accrued through depreciation rates and exclusive of ARO liabilities, of removing regulated property, plant and equipment in accordance with accepted regulatory practices. Amounts are deducted from rate base or otherwise accrue a carrying cost.