Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Foreign currency translation adjustments, income tax	$ 17	$ 1	$ 1
Foreign currency, reclassification to earnings, income tax benefit (expense)	0	0	0
Change in derivative fair value, income tax	10	(7)	16
Derivative reclassification to earnings, income tax benefit (expense)	(1)	(8)	(11)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Tax	(1)	(6)	0
Pension, net actuarial gain (loss) for the period, income tax	6	106	(29)
Pension, amortization of net actuarial loss, income tax benefit (expense)	$ (135)	$ (3)	$ (9)