The statutory corporate income tax rate for a foreign jurisdiction.

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The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate that can be explained by the tax effect of certain temporary differences due to state utility rate regulation.

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The carrying amount as of the balance sheet date of income taxes receivable from (payable to) related parties (typically the parent company) that are due within one year of the balance sheet date representing refunds of overpayments or recoveries based on agreed-upon resolutions of disputes with taxing authorities.

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The number of years from its in-service date that each wind-powered generating facility is eligible for federal renewable energy production tax credits.

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Amount of deferred state and local tax expense (benefit) pertaining to income (loss) from continuing operations.

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to statutory income tax expense (benefit) outside of the country of domicile.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to revisions of previously reported income tax expense.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax credits. Including, but not limited to, research credit, foreign tax credit, investment tax credit, and other tax credits.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, attributable to increase (decrease) in the income tax rates.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to revisions of previously reported income tax expense (benefit).

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Income Taxes Reconciliation of Effective Income Tax Rate (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended						1 Months Ended							12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 United Kingdom	Dec. 31, 2012 United Kingdom	Dec. 31, 2011 United Kingdom	Jul. 31, 2012 Corporate Income Tax Rate Enacted July 2012, Effective April 1, 2013 [Member] United Kingdom	Jul. 31, 2013 Corporate Income Tax Rate Enacted July 2013, Effective April 1, 2014 [Member] United Kingdom	Jul. 31, 2013 Corporate Income Tax Rate Enacted July 2013, Effective April 1, 2015 [Member] United Kingdom	Jul. 31, 2011 Corporate Income Tax Rate Enacted July 2011, Effective April 1, 2012 [Member] United Kingdom	Jul. 31, 2012 Corporate Income Tax Rate Enacted July 2012, Effective April 1, 2012 [Member] United Kingdom	Jul. 31, 2010 Corporate Income Tax Rate Enacted July 2010, Effective April 1, 2011 [Member] United Kingdom	Jul. 31, 2011 Corporate Income Tax Rate Enacted July 2011, Effective April 1, 2011 [Member] United Kingdom	Dec. 31, 2012 Repairs deduction [Member]	Dec. 31, 2011 Tax method Changes, Issue Resolutions [Member]	Dec. 31, 2013 NV Energy Transaction [Member]
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Federal statutory income tax rate	35.00%	35.00%	35.00%
Income tax credits	(14.00%)	(14.00%)	(11.00%)
State income tax, net of federal income tax benefit	(9.00%)	(3.00%)	0.00%
Income tax effect of foreign income	(6.00%)	(7.00%)	(5.00%)
Income tax method changes	0.00%	(1.00%)	(2.00%)
Effects of ratemaking	(1.00%)	(1.00%)	0.00%
Other, net	2.00%	0.00%	1.00%
Effective income tax rate	7.00%	9.00%	18.00%
Production Tax Credit Carryforwards [Abstract]
Years Eligible For Renewable Energy Production Tax Credit	10 years
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred state	$ 247	$ 11	$ 11													$ 161
United Kingdom Corporate Income Tax Rate Change [Abstract]
Income Tax Reconciliation, Change in Enacted Tax Rate				54	38	40
Corporate Income Tax Rate, Foreign							23.00%	21.00%	20.00%	25.00%	24.00%	27.00%	26.00%
Income tax method change [Abstract]
Income tax benefits from tax method change														16	35
Related Party Tax Expense [Abstract]
Income taxes receivable from Berkshire Hathaway	$ 25	$ 336