Consolidated Company-Sponsored Investment Funds - Change in Carrying Value Associated with Level 3 Financial Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair value measurement Level 3 reconciliation [Abstract]
Balance as of beginning of period	$ 114	$ 117	$ 119	$ 142
Purchases	0	0	0	0
Sales	0	0	0	0
Realized gains (losses), net	0	0	0	0
Unrealized gains (losses), net	7	1	2	(24)
Balance as of end of period	121	118	121	118
Company-sponsored investment funds
Fair value measurement Level 3 reconciliation [Abstract]
Balance as of beginning of period	517	11,834	854	8,373
Deconsolidated funds	0	0	(135)	0
Transfers (out) in	(6)	(3,602)	565	(3,788)
Purchases	61	1,187	107	8,978
Sales	(7)	(2,996)	(451)	(7,345)
Realized gains (losses), net	(7)	12	(21)	35
Unrealized gains (losses), net	39	(40)	(323)	129
Accrued discounts	0	6	1	19
Balance as of end of period	$ 597	$ 6,401	$ 597	$ 6,401