Changes in Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Changes in Other Comprehensive Income [Abstract]
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	$ (54)	$ (38)	$ (16)
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges and Treasury Locks, Effect Net of Tax	152	219	141
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	(10)	(37)	(19)
Accumulated Other Comprehensive Income (Loss), Net of Tax	88	144	106
Cumulative Translation Adjustment, Net of Tax, Period Increase (Decrease)	(16)	(22)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Before Reclassifications, Net of Tax	70	145
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, before Reclassification Adjustments, Net of Tax	(3)	(10)
Other Comprehensive Income (Loss), Amortization, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Recognized in Net Periodic Pension Cost, Net of Tax	30	(8)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	27	(18)	22
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	51	113
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Reclassified from OCI, Net of Tax	(137)	(67)
Other Comprehensive Income (Loss), Reclassifications out of OCI, Net of Tax	(107)	(75)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(16)	(22)	10
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	(67)	78	107
Other comprehensive income for defined benefits and pension items, before reclassification, tax impact	2	5
Other Comprehensive Income (Loss), Net of Tax	(56)	38	$ 139
Other Comprehensive Income (Loss), Tax	(39)	(83)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising Reclassed from OCI, Tax	78	38
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized (Gain) Loss Arising During Period, Tax	$ 17	$ 5