Changes in Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Changes in Other Comprehensive Income [Abstract]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	$ 16	$ 17	$ 53	$ 1
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	(18)	(49)	(18)	(49)	(26)	(58)
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	115	(31)	115	(31)	34	(48)
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	(41)	(32)	(41)	(32)	(41)	(32)
Accumulated Other Comprehensive Income (Loss), Net of Tax	56	(112)	56	(112)	(33)	(138)
Cumulative Translation Adjustment, Net of Tax, Period Increase (Decrease)			8	9
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Before Reclassifications, Net of Tax			91	0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			99	9
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Reclassified from OCI, Net of Tax			(10)	17
Other Comprehensive Income (Loss), Reclassifications out of OCI, Net of Tax			(10)	17
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	10	2	8	9
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	(38)	(27)	81	17
Other Comprehensive Income (Loss), Net of Tax	(28)	(25)	89	26
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising Reclassed from OCI, Tax	$ 6	$ 1	$ 5	$ 9