Investment Securities - Investment securities and summary of the gains (losses) related to securities (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Available for sale securities:
Amortized cost		$ 129,692
Unrealized gains		1,133
Unrealized losses		(7,449)
Fair value	$ 120,756	123,376
Trading securities:
Fair value	164,561	175,365
Equity method securities
Equity method securities	23,986	30,009
Total investment securities	309,303	328,750
Sponsored funds
Available for sale securities:
Amortized cost	124,954	129,427
Unrealized gains	1,258	828
Unrealized losses	(5,456)	(7,449)
Fair value	120,756	122,806
Trading securities:
Fair value	30,555	29,541
Equity method securities
Equity method securities	20,441	26,775
Sponsored privately offered funds
Available for sale securities:
Amortized cost		265
Unrealized gains		305
Fair value		570
Trading securities:
Fair value	614
Equity method securities
Equity method securities	3,545	3,234
Mortgage-backed securities
Trading securities:
Fair value	12	13
Common Stock
Trading securities:
Fair value	104	101
Consolidated Sponsored Funds
Trading securities:
Fair value	$ 133,276	$ 145,710

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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