Income Taxes - Additional Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Income Taxes Other Information [Line Items]
Income Tax Expense (Benefit)	$ 191us-gaap_IncomeTaxExpenseBenefit	$ 125us-gaap_IncomeTaxExpenseBenefit
Effective Income Tax Rate Reconciliation, Percent	31.00%	24.00%
Unrecognized Tax Benefits	213us-gaap_UnrecognizedTaxBenefits		210us-gaap_UnrecognizedTaxBenefits
Significant (Increase) Decrease in Unrecognized Tax Benefits is Reasonably Possible, Estimated Range of Change, Upper Bound	$ 115

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

+ References

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-Publisher FASB

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

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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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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