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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Fair value measurement Level 3 reconciliation [Abstract]
Balance as of beginning of period	$ 5,028	$ 4,938	$ 5,023	$ 16,148
Transfers in (out)	0	0	0	(9,532)
Purchases	0	0	0	0
Sales	0	0	0	0
Realized (losses), net	0	0	0	0
Unrealized gains (losses), net	(3,958)	2	(3,953)	(1,676)
Balance as of end of period	1,070	4,940	1,070	4,940
Company-sponsored investment funds
Fair value measurement Level 3 reconciliation [Abstract]
Balance as of beginning of period	2,797	13,108	5,741	0
Impact of adoption of ASU 2015-02	0	0	0	14,740
Deconsolidated funds	0	(1,403)	(6,697)	(1,403)
Transfers in (out)	(35)	(23,566)	378	(24,881)
Purchases	346	640	5,358	996
Sales	(1,148)	(278)	(3,045)	(786)
Realized (losses), net	5	15	1	(24)
Unrealized gains (losses), net	52	14,243	269	14,120
Accrued discounts	1	0	13	(3)
Balance as of end of period	$ 2,018	$ 2,759	$ 2,018	$ 2,759