Investment Securities - Fair value of investment securities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair value of investments
Available-for-sale Securities	$ 125,364	$ 41,377
Trading Securities	153,508	29,813
Equity method securities	40,375	220,553
Total investment securities	319,247	291,743
Total
Fair value of investments
Total investment securities	319,247	291,743
Sponsored funds
Fair value of investments
Available-for-sale Securities	124,812	40,552
Trading Securities	29,597	29,701
Equity method securities	37,100	217,380
Sponsored funds \| Total
Fair value of investments
Available-for-sale Securities	124,812	40,552
Trading Securities	29,597	29,701
Equity method securities	37,100	217,380
Sponsored privately offered funds measured at net asset value
Fair value of investments
Available-for-sale Securities	552	825
Equity method securities	3,275	3,173
Sponsored privately offered funds measured at net asset value \| Total
Fair value of investments
Available-for-sale Securities	552	825
Equity method securities	3,275	3,173
Mortgage-backed securities
Fair value of investments
Trading Securities	15	20
Mortgage-backed securities \| Total
Fair value of investments
Trading Securities	15	20
Corporate bonds
Fair value of investments
Trading Securities	3	5
Corporate bonds \| Total
Fair value of investments
Trading Securities	3	5
Common Stock
Fair value of investments
Trading Securities	101	87
Common Stock \| Total
Fair value of investments
Trading Securities	101	87
Consolidated Sponsored Funds
Fair value of investments
Trading Securities	123,792
Consolidated Sponsored Funds \| Total
Fair value of investments
Trading Securities	123,792
Level 1
Fair value of investments
Total investment securities	279,003	287,720
Level 1 \| Sponsored funds
Fair value of investments
Available-for-sale Securities	124,812	40,552
Trading Securities	29,597	29,701
Equity method securities	37,100	217,380
Level 1 \| Common Stock
Fair value of investments
Trading Securities	101	87
Level 1 \| Consolidated Sponsored Funds
Fair value of investments
Trading Securities	87,393
Level 2
Fair value of investments
Total investment securities	36,417	25
Level 2 \| Mortgage-backed securities
Fair value of investments
Trading Securities	15	20
Level 2 \| Corporate bonds
Fair value of investments
Trading Securities	3	$ 5
Level 2 \| Consolidated Sponsored Funds
Fair value of investments
Trading Securities	$ 36,399

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount of investments in debt and equity securities, including, but not limited to, held-to-maturity, trading and available-for-sale expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer.

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Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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