Summary of Accounting Policies - Error Correction, Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income	$ 45	$ 63	$ (60)	$ 137
Foreign currency translation adjustments	(18)	(99)	17	(72)
Defined benefit plans	(2)	4	(1)	7
Other comprehensive income (loss) — net of tax	(23)	(95)	17	(65)
Comprehensive income (loss)	22	(32)	(43)	72
Less: Comprehensive income (loss) attributable to noncontrolling interests	18	9	36	31
Comprehensive income (loss) attributable to common shareholders	$ 4	(41)	$ (79)	41
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income		66		138
Foreign currency translation adjustments		(100)		(73)
Defined benefit plans		4		7
Other comprehensive income (loss) — net of tax		(96)		(66)
Comprehensive income (loss)		(30)		72
Less: Comprehensive income (loss) attributable to noncontrolling interests		9		31
Comprehensive income (loss) attributable to common shareholders		(39)		41
Reclasses
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income		0		0
Foreign currency translation adjustments		0		0
Defined benefit plans		0		0
Other comprehensive income (loss) — net of tax		0		0
Comprehensive income (loss)		0		0
Less: Comprehensive income (loss) attributable to noncontrolling interests		0		0
Comprehensive income (loss) attributable to common shareholders		0		0
As Reclassified
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income		66		138
Foreign currency translation adjustments		(100)		(73)
Defined benefit plans		4		7
Other comprehensive income (loss) — net of tax		(96)		(66)
Comprehensive income (loss)		(30)		72
Less: Comprehensive income (loss) attributable to noncontrolling interests		9		31
Comprehensive income (loss) attributable to common shareholders		(39)		41
Revisions
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income		(3)		(1)
Foreign currency translation adjustments		1		1
Defined benefit plans		0		0
Other comprehensive income (loss) — net of tax		1		1
Comprehensive income (loss)		(2)		0
Less: Comprehensive income (loss) attributable to noncontrolling interests		0		0
Comprehensive income (loss) attributable to common shareholders		$ (2)		$ 0