Income Taxes (Consolidated Income Tax Expense) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Federal	$ 225us-gaap_CurrentFederalTaxExpenseBenefit	$ 121us-gaap_CurrentFederalTaxExpenseBenefit	$ 47us-gaap_CurrentFederalTaxExpenseBenefit
State and local	13	6	(4)
Total current provision	238us-gaap_CurrentIncomeTaxExpenseBenefit	127us-gaap_CurrentIncomeTaxExpenseBenefit	43us-gaap_CurrentIncomeTaxExpenseBenefit
Deferred provision	(42)us-gaap_DeferredOtherTaxExpenseBenefit	(20)us-gaap_DeferredOtherTaxExpenseBenefit	4us-gaap_DeferredOtherTaxExpenseBenefit
Income tax expense	$ 196us-gaap_IncomeTaxExpenseBenefit	$ 107us-gaap_IncomeTaxExpenseBenefit	$ 47us-gaap_IncomeTaxExpenseBenefit

Amount of current federal tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of current income tax expense (benefit) pertaining to taxable income (loss) from continuing operations.

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

Amount of other deferred income tax expense (benefit) pertaining to income (loss) from continuing operations. For example, but not limited to, acquisition-date income tax benefits or expenses recognized from changes in the acquirer's valuation allowance for its previously existing deferred tax assets resulting from a business combination and adjustments to beginning-of-year balance of a valuation allowance because of a change in circumstance causing a change in judgment about the realizability of the related deferred tax asset in future periods.

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