Investment Securities - Fair value of investment securities (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Fair value of investments
Available-for-sale Securities	$ 123,376	$ 41,377
Trading Securities	175,365	29,813
Equity method securities	30,009	220,553
Total investment securities	328,750	291,743
Amount of transfer between levels	0	0
Total
Fair value of investments
Total investment securities	328,750	291,743
Sponsored funds
Fair value of investments
Available-for-sale Securities	122,806	40,552
Trading Securities	29,541	29,701
Equity method securities	26,775	217,380
Sponsored funds \| Total
Fair value of investments
Available-for-sale Securities	122,806	40,552
Trading Securities	29,541	29,701
Equity method securities	26,775	217,380
Sponsored privately offered funds
Fair value of investments
Available-for-sale Securities	570	825
Equity method securities	3,234	3,173
Total investment securities	3,800	4,000
Sponsored privately offered funds \| Total
Fair value of investments
Available-for-sale Securities	570	825
Equity method securities	3,234	3,173
Mortgage-backed securities
Fair value of investments
Trading Securities	13	20
Mortgage-backed securities \| Total
Fair value of investments
Trading Securities	13	20
Corporate bonds
Fair value of investments
Trading Securities		5
Corporate bonds \| Total
Fair value of investments
Trading Securities		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	145,710
Consolidated Sponsored Funds \| Total
Fair value of investments
Trading Securities	145,710
Level 1
Fair value of investments
Total investment securities	280,070	287,720
Level 1 \| Sponsored funds
Fair value of investments
Available-for-sale Securities	122,806	40,552
Trading Securities	29,541	29,701
Equity method securities	26,775	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	100,847
Level 2
Fair value of investments
Total investment securities	44,876	25
Level 2 \| Mortgage-backed securities
Fair value of investments
Trading Securities	13	20
Level 2 \| Corporate bonds
Fair value of investments
Trading Securities		5
Level 2 \| Consolidated Sponsored Funds
Fair value of investments
Trading Securities	44,863
Other Assets Not Held at Fair Value
Fair value of investments
Total investment securities	3,804	3,998
Other Assets Not Held at Fair Value \| Sponsored privately offered funds
Fair value of investments
Available-for-sale Securities	570	825
Equity method securities	$ 3,234	$ 3,173

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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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