Derivative Instruments (Change in Unrealized (Losses) Gains in Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Net unrealized gains (losses) on cash flow hedges, net of taxes, beginning of period			$ 194
Net unrealized gains (losses) on cash flow hedges, net of taxes, end of period	$ 462		462
Unrealized Gain (Loss) on Forward Exchange Contracts
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Net unrealized gains (losses) on cash flow hedges, net of taxes, beginning of period	1	$ (1)	(1)	$ (1)
Change in fair value, net of tax	2	0	6	0
Reclassification into earnings, net of tax	(1)	0	(3)	0
Net unrealized gains (losses) on cash flow hedges, net of taxes, end of period	$ 2	$ (1)	$ 2	$ (1)