Provision for Income Taxes (Reconciliation of Amounts of Unrecognized Tax Benefits) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Disclosure [Abstract]
Total Unrecognized Tax Benefits as of January 1	$ 800	$ 693	$ 739
Gross amounts of decreases in unrecognized tax benefits as a result of tax positions taken during the prior period	(94)	(82)	(155)
Gross amounts of increases in unrecognized tax benefits as a result of tax positions taken during the prior period	73	170	169
Gross amounts of increases in unrecognized tax benefits as a result of tax positions taken during the current period	78	79	51
Amount of decreases in unrecognized tax benefits relating to settlements with taxing authorities	(29)	(6)	(90)
Reduction to unrecognized tax benefits as a result of a lapse of the applicable statute of limitations	(10)	(32)	(24)
Exchange gain (loss)	(13)	(22)	3
Total Unrecognized Tax Benefits as of December 31	805	800	693
Total unrecognized tax benefits that, if recognized, would impact the effective tax rate	693	683	545
Total amount of interest and penalties recognized in the Consolidated Income Statements	4	7	(70)
Total amount of interest and penalties recognized in the Consolidated Balance Sheets	$ 116	$ 113	$ 99