Non-controlling Interests (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Noncontrolling Interest [Line Items]
Non-redeemable non-controlling interests	$ 71	$ 12,642	$ 9,681	$ 5,689
Total non-controlling interest in net income (loss)	16,526	15,696	50,013	14,791
Non-redeemable non-controlling interest	1,607		1,607		$ 36,172
Redeemable non-controlling interest	421,618		421,618		392,959
CPH acquisition
Noncontrolling Interest [Line Items]
Redeemable non-controlling interest	5,364		5,364		8,665
Other
Noncontrolling Interest [Line Items]
Non-redeemable non-controlling interests	50	143	245	343
Non-redeemable non-controlling interest	766		766		1,550
Company-sponsored investment funds
Noncontrolling Interest [Line Items]
Non-redeemable non-controlling interests	21	12,499	9,436	5,346
Redeemable non-controlling interests	16,455	$ 3,054	40,332	$ 9,102
Non-redeemable non-controlling interest	841		841		34,622
Redeemable non-controlling interest	$ 416,254		$ 416,254		$ 384,294