Income Taxes - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Income Taxes Other Information [Line Items]
Income Tax Expense (Benefit)	$ 202	$ 173	$ 393	$ 298
Effective Income Tax Rate Reconciliation, Percent	29.00%	30.00%	30.00%	27.00%
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	$ 15
Unrecognized Tax Benefits	216		$ 216		$ 210
Significant (Increase) Decrease in Unrecognized Tax Benefits is Reasonably Possible, Estimated Range of Change, Upper Bound	$ 120		$ 120

[Line Items] for Income Taxes Other Information [Table]

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

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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 other adjustments.

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Amount of (increase) decrease reasonably possible in the estimated upper bound of the unrecognized tax benefit for a tax position taken or expected to be taken.

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Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

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