Derivative Instruments (Effective Portion of Unrealized Gain (Loss)) (Details) - Derivatives in cash flow hedging relationships [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Effective portion of the unrealized gain (loss) recognized in Other Comprehensive Income for our derivative instruments designated as cash flow hedges contracts [Abstract]
Unrealized gain (loss) on derivative instruments recognized in Other Comprehensive Income, effective portion, net	$ (176)	$ 150	$ 298
Foreign currency contracts [Member]
Effective portion of the unrealized gain (loss) recognized in Other Comprehensive Income for our derivative instruments designated as cash flow hedges contracts [Abstract]
Unrealized gain (loss) on derivative instruments recognized in Other Comprehensive Income, effective portion, net	115	425	452
Cross-currency swap contracts [Member]
Effective portion of the unrealized gain (loss) recognized in Other Comprehensive Income for our derivative instruments designated as cash flow hedges contracts [Abstract]
Unrealized gain (loss) on derivative instruments recognized in Other Comprehensive Income, effective portion, net	(281)	(275)	(154)
Forward interest rate contract [Member]
Effective portion of the unrealized gain (loss) recognized in Other Comprehensive Income for our derivative instruments designated as cash flow hedges contracts [Abstract]
Unrealized gain (loss) on derivative instruments recognized in Other Comprehensive Income, effective portion, net	$ (10)	$ 0	$ 0