Income Taxes (Schedule of Unrecognized Tax Benefits Roll Forward) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	$ 1,141us-gaap_UnrecognizedTaxBenefits	$ 1,055us-gaap_UnrecognizedTaxBenefits	$ 939us-gaap_UnrecognizedTaxBenefits
Gross increases – tax positions in prior periods	403	10	55
Gross decreases – tax positions in prior periods	(251)	(125)	(20)
Gross increases – current-period tax positions	217	202	83
Gross decreases – current-period tax positions		(1)	(1)
Settlements	(197)		(1)
Lapse of statute of limitations	(1)
Unrecognized tax benefits – December 31	$ 1,312us-gaap_UnrecognizedTaxBenefits	$ 1,141us-gaap_UnrecognizedTaxBenefits	$ 1,055us-gaap_UnrecognizedTaxBenefits

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

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Amount of decrease in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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