Redeemable Noncontrolling Interests - Schedule of Redeemable Noncontrolling Interest (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Increase (Decrease) in Redeemable Non-controlling Interests [Roll Forward]
Balance at December 31, 2017	$ 4,178
Business acquisition	55,500
Net income (loss)	515	$ 1,420	$ 261
Net subscriptions (redemptions) (distributions) and other	(2,712)
Balance at December 31, 2018	57,481	4,178
Consolidated investment products
Increase (Decrease) in Redeemable Non-controlling Interests [Roll Forward]
Balance at December 31, 2017	4,178
Business acquisition	0
Net income (loss)	(472)
Net subscriptions (redemptions) (distributions) and other	(1,322)
Balance at December 31, 2018	2,384	4,178
Affiliate Noncontrolling Interests
Increase (Decrease) in Redeemable Non-controlling Interests [Roll Forward]
Balance at December 31, 2017	0
Business acquisition	55,500
Net income (loss)	987
Net subscriptions (redemptions) (distributions) and other	(1,390)
Balance at December 31, 2018	$ 55,097	$ 0