Redeemable Noncontrolling Interests - Reconciliation of Changes in Redeemable Noncontrolling Interests (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Increase (Decrease) in Temporary Equity [Roll Forward]
Balance, beginning of period	$ 47,000,000	$ 0
Initial fair value of redeemable noncontrolling interests of acquired businesses	102,000,000	44,000,000
Capital contribution from redeemable noncontrolling interest	3,000,000
Purchase of redeemable noncontrolling interest	(46,000,000)	(1,000,000)
Net income (loss) attributable to redeemable noncontrolling interests		(5,000,000)
Other comprehensive income (loss) attributable to redeemable noncontrolling interests	(6,000,000)	3,000,000
Adjustment to redemption value		6,000,000
Balance, end of period	$ 100,000,000	$ 47,000,000