Summary of Accounting Policies - Error Correction, Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income	$ 111	$ 265	$ 415
Foreign currency translation adjustment	(134)	106	(56)
Defined benefit plans	(22)	17	51
Other comprehensive income (loss), net of tax	(156)	123	(5)
Comprehensive income (loss)	(45)	388	410
Less: Comprehensive income (loss) attributable to noncontrolling interests	54	69	64
Comprehensive income (loss) attributable to common shareholders	$ (99)	319	346
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income		274	424
Foreign currency translation adjustment		99	(45)
Defined benefit plans		27	41
Other comprehensive income (loss), net of tax		126	(4)
Comprehensive income (loss)		400	420
Less: Comprehensive income (loss) attributable to noncontrolling interests		69	64
Comprehensive income (loss) attributable to common shareholders		331	356
Revisions
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income		(9)	(9)
Foreign currency translation adjustment		7	(11)
Defined benefit plans		(10)	10
Other comprehensive income (loss), net of tax		(3)	(1)
Comprehensive income (loss)		(12)	(10)
Comprehensive income (loss) attributable to common shareholders		(12)	(10)
As Reclassified
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income		274	424
Foreign currency translation adjustment		99	(45)
Defined benefit plans		27	41
Other comprehensive income (loss), net of tax		126	(4)
Comprehensive income (loss)		400	420
Less: Comprehensive income (loss) attributable to noncontrolling interests		69	64
Comprehensive income (loss) attributable to common shareholders		$ 331	$ 356