Equity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at the beginning of the period	$ (1,071)	$ (1,102)	$ (782)
Other comprehensive (loss) income before reclassification adjustments	52	(13)	(367)
Amount reclassified from accumulated OCI	(4)	(50)	(47)
Tax benefit (provision)	2	(6)
Net other comprehensive income (loss)	58	31	(320)
Balance at end of the period	(1,013)	(1,071)	(1,102)
Cumulative Translation Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at the beginning of the period	(1,008)	(1,025)	(701)
Other comprehensive (loss) income before reclassification adjustments	57	17	(324)
Net other comprehensive income (loss)	57	17	(324)
Balance at end of the period	(951)	(1,008)	(1,025)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at the beginning of the period	(7)	(29)	(19)
Other comprehensive (loss) income before reclassification adjustments	(16)	(17)	(61)
Amount reclassified from accumulated OCI	(6)	(49)	(46)
Tax benefit (provision)	4	(10)	5
Net other comprehensive income (loss)	(6)	22	(10)
Balance at end of the period	(13)	(7)	(29)
Pension and Postretirement Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at the beginning of the period	(56)	(47)	(61)
Other comprehensive (loss) income before reclassification adjustments	8	(14)	18
Amount reclassified from accumulated OCI	2	(1)	(1)
Tax benefit (provision)	(1)	4	(5)
Net other comprehensive income (loss)	5	(9)	14
Balance at end of the period	(51)	(56)	(47)
Unrealized (Loss) Gain on Investment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at the beginning of the period		(1)	(1)
Other comprehensive (loss) income before reclassification adjustments	3	1
Tax benefit (provision)	(1)
Net other comprehensive income (loss)	2	$ 1
Balance at end of the period	$ 2		$ (1)