Stockholders' Equity - Changes in Equity (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 1,814	$ 1,251	$ 1,442	$ 1,114
Net income	112	96	147	334
Net income	114	96	150	333
Other comprehensive income (loss)	(33)	5	364	(42)
Other comprehensive income (loss) including portion attributable to nonredeemable noncontrolling interest	(38)	5	355	(41)
Common stock dividends	(15)	(14)	(44)	(44)
Distributions to noncontrolling interests	(2)	(3)	(14)	(7)
Increase from business combination			8
Purchase of noncontrolling interests				0
Purchase of redeemable noncontrolling interests		2		2
Contribution from noncontrolling interest		22		22
Common stock share repurchases			(25)	(25)
Stock compensation	5	6	13	17
Stock withheld for employee taxes		(1)	(6)	(7)
Ending Balance	1,878	1,364	1,878	1,364
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	2	2	2	2
Ending Balance	2	2	2	2
Additional Paid-in Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	2,376	2,356	2,368	2,354
Purchase of noncontrolling interests				(9)
Purchase of redeemable noncontrolling interests		2		2
Stock compensation	5	6	13	17
Ending Balance	2,381	2,364	2,381	2,364
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	456	290	456	86
Net income	111	95	141	327
Common stock dividends	(15)	(14)	(44)	(44)
Ending Balance	552	371	552	371
Treasury Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(150)	(118)	(119)	(87)
Common stock share repurchases			(25)	(25)
Stock withheld for employee taxes		(1)	(6)	(7)
Ending Balance	(150)	(119)	(150)	(119)
AOCI Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(968)	(1,385)	(1,362)	(1,342)
Other comprehensive income (loss)	(26)	6	368	(35)
Ending Balance	(994)	(1,379)	(994)	(1,379)
Non-Controlling Interests [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	98	106	97	101
Net income	3	1	9	6
Other comprehensive income (loss)	(12)	(1)	(13)	(6)
Distributions to noncontrolling interests	(2)	(3)	(14)	(7)
Increase from business combination			8
Purchase of noncontrolling Interests				9
Contribution from noncontrolling interest		22		22
Ending Balance	$ 87	$ 125	$ 87	$ 125
Accounting Standards Update 2016-02 [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact on retained earnings					$ (1)
Accounting Standards Update 2016-02 [Member] | Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact on retained earnings					$ (1)
Accounting Standards Update 2016-01 [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact on retained earnings						$ 0
Accounting Standards Update 2016-01 [Member] | Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact on retained earnings						2
Accounting Standards Update 2016-01 [Member] | AOCI Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact on retained earnings						$ (2)