Asset Retirement Obligations - SPPC - Asset Retirement Obligation by Type (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Asset Retirement Obligations By Type [Line Items]
Regulatory Liabilities		$ 3,033	$ 2,832
Asset Retirement Obligation		921	753	$ 696
Other Plant in Service [Member]
Asset Retirement Obligations By Type [Line Items]
Asset Retirement Obligation		42	39
Removal Costs [Member]
Asset Retirement Obligations By Type [Line Items]
Regulatory Liabilities	[1]	2,167	2,215
Sierra Pacific Power Company [Member]
Asset Retirement Obligations By Type [Line Items]
Regulatory Liabilities		308	301
Asset Retirement Obligation		10	11	$ 16
Sierra Pacific Power Company [Member] | Asbestos [Member]
Asset Retirement Obligations By Type [Line Items]
Asset Retirement Obligation		4	5
Sierra Pacific Power Company [Member] | Evaporative Ponds and Dry Ash Landfills [Member]
Asset Retirement Obligations By Type [Line Items]
Asset Retirement Obligation		3	2
Sierra Pacific Power Company [Member] | Other Plant in Service [Member]
Asset Retirement Obligations By Type [Line Items]
Asset Retirement Obligation		3	4
Sierra Pacific Power Company [Member] | Removal Costs [Member]
Asset Retirement Obligations By Type [Line Items]
Regulatory Liabilities	[2]	$ 208	$ 233

[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.