Stockholders' Equity - Changes in Equity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 1,442	$ 1,114
Net income	101	111
Net income	102	110
Other comprehensive income	37	9
Other comprehensive income including portion attributable to nonredeemable noncontrolling interest	32	8
Common stock dividends	(15)	(15)
Distributions to noncontrolling interests	(1)	(1)
Increase from business combination	7
Purchase of noncontrolling interests		0
Common stock share repurchases	(25)
Stock compensation	4	5
Stock withheld for employee taxes	(6)	(6)
Ending Balance	1,539	1,215
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	2	2
Ending Balance	2	2
Additional Paid-in Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	2,368	2,354
Purchase of noncontrolling interests		(9)
Stock compensation	4	5
Ending Balance	2,372	2,350
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	456	86
Net income	98	108
Common stock dividends	(15)	(15)
Ending Balance	538	181
Treasury Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(119)	(87)
Common stock share repurchases	(25)
Stock withheld for employee taxes	(6)	(6)
Ending Balance	(150)	(93)
AOCI Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(1,362)	(1,342)
Other comprehensive income	34	8
Ending Balance	(1,328)	(1,336)
Non-Controlling Interests [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	97	101
Net income	4	2
Other comprehensive income	(2)
Distributions to noncontrolling interests	(1)	(1)
Increase from business combination	7
Purchase of noncontrolling Interests		9
Ending Balance	$ 105	$ 111
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)