Regulatory Matters - SPPC - Regulatory Liabilities - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 3,033	$ 2,832
Regulatory liabilities		402	163
Regulatory liabilities		2,631	2,669
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[1]	2,167	2,215
Regulatory liabilities other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		301	259
Sierra Pacific Power Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		308	301
Regulatory liabilities		78	39
Regulatory liabilities		$ 230	262
Sierra Pacific Power Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		40 years
Regulatory Liabilities	[2]	$ 208	233
Sierra Pacific Power Company [Member] | Deferred Excess Energy Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		2 years
Regulatory Liabilities		$ 66	0
Sierra Pacific Power Company [Member] | Renewable Energy Program [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		1 year
Regulatory Liabilities		$ 8	32
Sierra Pacific Power Company [Member] | Regulatory liabilities other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 26	$ 36

[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.