Provision for Income Taxes (Reconciliation of Amounts of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Total unrecognized tax benefits as of January 1	$ 986	$ 901	$ 805
Gross amounts of decreases in unrecognized tax benefits as a result of tax positions taken during the prior period	(98)	(50)	(28)
Gross amounts of increases in unrecognized tax benefits as a result of tax positions taken during the prior period	13	84	76
Gross amounts of increases in unrecognized tax benefits as a result of tax positions taken during the current period	69	92	92
Amount of decreases in the unrecognized tax benefits relating to settlements	(58)	(15)	(19)
Reduction to unrecognized tax benefits as a result of a lapse of the applicable statute of limitations	(30)	(3)	(6)
Exchange gain	(36)	(23)	(19)
Total unrecognized tax benefits as of December 31	846	986	901
Total unrecognized tax benefits that, if recognized, would impact the effective tax rate	651	818	778
Total amount of interest and penalties recognized in the Consolidated Income Statements	5	5	16
Total amount of interest and penalties recognized in the Consolidated Balance Sheets	$ 100	$ 117	$ 122