Redeemable Non-Controlling Interests in Consolidated Subsidiaries and Funds (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Noncontrolling Interest [Line Items]
Redeemable non-controlling interests in consolidated subsidiaries and funds	$ 440,312		$ 440,312		$ 284,780
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	4,331	$ 24,607	6,537	$ 35,763
Operating Entities
Noncontrolling Interest [Line Items]
Redeemable non-controlling interests in consolidated subsidiaries and funds	22,857		22,857		10,434
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	853	1,954	2,659	3,574
Consolidated Funds
Noncontrolling Interest [Line Items]
Redeemable non-controlling interests in consolidated subsidiaries and funds	417,455		417,455		$ 274,346
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	$ 3,478	$ 22,653	$ 3,878	$ 32,189