Investment Securities - Investment securities and summary of the gains (losses) related to securities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Available for sale securities:
Amortized cost	$ 129,670	$ 47,300
Unrealized gains	1,011	759
Unrealized losses	(5,317)	(6,682)
Fair value	125,364	41,377
Trading securities:
Fair value	153,508	29,813
Equity method securities
Equity method securities	40,375	220,553
Total investment securities	319,247	291,743
Sponsored funds
Available for sale securities:
Amortized cost	129,406	46,800
Unrealized gains	723	434
Unrealized losses	(5,317)	(6,682)
Fair value	124,812	40,552
Trading securities:
Fair value	29,597	29,701
Equity method securities
Equity method securities	37,100	217,380
Sponsored privately offered funds measured at net asset value
Available for sale securities:
Amortized cost	264	500
Unrealized gains	288	325
Fair value	552	825
Equity method securities
Equity method securities	3,275	3,173
Mortgage-backed securities
Trading securities:
Fair value	15	20
Corporate bonds
Trading securities:
Fair value	3	5
Common Stock
Trading securities:
Fair value	101	$ 87
Consolidated Sponsored Funds
Trading securities:
Fair value	$ 123,792

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

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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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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