Asset Retirement Obligations - NPC - 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
Nevada Power Company [Member]
Asset Retirement Obligations By Type [Line Items]
Regulatory Liabilities		477	366
Asset Retirement Obligation		85	86	$ 100
Nevada Power Company [Member] | Waste water remediation [Member]
Asset Retirement Obligations By Type [Line Items]
Asset Retirement Obligation		42	53
Nevada Power Company [Member] | Evaporative Ponds and Dry Ash Landfills [Member]
Asset Retirement Obligations By Type [Line Items]
Asset Retirement Obligation		27	25
Nevada Power Company [Member] | Asbestos [Member]
Asset Retirement Obligations By Type [Line Items]
Asset Retirement Obligation		3	3
Nevada Power Company [Member] | Other Plant in Service [Member]
Asset Retirement Obligations By Type [Line Items]
Asset Retirement Obligation		13	5
Removal Costs [Member]
Asset Retirement Obligations By Type [Line Items]
Regulatory Liabilities	[1]	2,167	2,215
Removal Costs [Member] | Nevada Power Company [Member]
Asset Retirement Obligations By Type [Line Items]
Regulatory Liabilities	[2]	$ 273	$ 295

[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.