Regulatory Matters - NPC - Regulatory Liabilities (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 7,511	$ 3,120
Regulatory liabilities		202	187
Regulatory liabilities		$ 7,309	$ 2,933
Federal statutory income tax rate		35.00%	35.00%	35.00%
Deferred Income Tax Charge [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years	[1]	Various
Regulatory Liabilities	[1]	$ 4,143	$ 25
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years	[2]	26.845466155811
Regulatory Liabilities	[2]	$ 2,349	2,242
Impact fees [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		6
Regulatory Liabilities		$ 89	90
Regulatory liabilities other [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		Various
Regulatory Liabilities		$ 341	302
Nevada Power Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,121	453
Regulatory liabilities		91	37
Regulatory liabilities		$ 1,030	$ 416
Federal statutory income tax rate		35.00%	35.00%	35.00%
Nevada Power Company [Member] | Deferred Income Taxes [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years	[3]	P33Y
Nevada Power Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[3]	$ 670	$ 9
Nevada Power Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years	[4]	P31Y
Regulatory Liabilities	[4]	$ 307	294
Nevada Power Company [Member] | Impact fees [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		P6Y
Regulatory Liabilities		$ 89	90
Nevada Power Company [Member] | Energy Efficiency Program [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		P1Y
Regulatory Liabilities		$ 27	37
Nevada Power Company [Member] | Regulatory liabilities other [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		Various
Regulatory Liabilities		$ 28	$ 23
Tax Cuts and Jobs Act of 2017 [Member]
Regulatory Liabilities [Line Items]
Federal statutory income tax rate		21.00%
Tax Cuts and Jobs Act of 2017 [Member] | Deferred Income Tax Charge [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[3]	$ 5,950
Tax Cuts and Jobs Act of 2017 [Member] | Nevada Power Company [Member]
Regulatory Liabilities [Line Items]
Federal statutory income tax rate		21.00%
Tax Cuts and Jobs Act of 2017 [Member] | Nevada Power Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[3]	$ 792

[1] (1)Amounts primarily represent income tax liabilities related to the federal tax rate change from 35% to 21% that are probable to be passed on to customers, offset by income tax benefits related to certain property-related basis differences and other various differences that were previously passed on to customers and will be included in regulated rates when the temporary differences reverse. See Note 11 for further discussion of 2017 Tax Reform impacts.

[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.

[3] (1)Amounts primarily represent income tax liabilities related to the federal tax rate change from 35% to 21% that are probable to be passed on to customers, offset by income tax benefits related to accelerated tax depreciation and certain property-related basis differences that were previously passed on to customers and will be included in regulated rates when the temporary differences reverse. See Note 10 for further discussion of 2017 Tax Reform impacts.

[4] (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.