Provision for Income Taxes (Reconciliation of Amounts of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Total unrecognized tax benefits as of January 1	$ 846	$ 986	$ 901
Gross amounts of decreases in unrecognized tax benefits as a result of tax positions taken during the prior period	(41)	(98)	(50)
Gross amounts of increases in unrecognized tax benefits as a result of tax positions taken during the prior period	32	13	84
Gross amounts of increases in unrecognized tax benefits as a result of tax positions taken during the current period	55	69	92
Amount of decreases in the unrecognized tax benefits relating to settlements	(314)	(58)	(15)
Reduction to unrecognized tax benefits as a result of a lapse of the applicable statute of limitations	(30)	(30)	(3)
Exchange loss (gain)	2	(36)	(23)
Total unrecognized tax benefits as of December 31	550	846	986
Total unrecognized tax benefits that, if recognized, would impact the effective tax rate	429	651	818
Total amount of interest and penalties recognized in the Consolidated Income Statements	20	(8)	5
Total amount of interest and penalties recognized in the Consolidated Balance Sheets	$ 98	$ 105	$ 117