Investment Securities - Investment securities and summary of the gains (losses) related to securities (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2016
Available for sale securities:
Amortized cost	$ 47,300	$ 129,692
Unrealized gains	759	1,133
Unrealized losses	(6,682)	(7,449)
Fair value	41,377	123,376
Trading securities:
Fair value	29,813	175,365
Unrealized losses	2,100
Equity method securities
Equity method securities	220,553	30,009
Total investment securities	291,743	328,750
Transfers to equity method securities	160,200
Sponsored funds
Available for sale securities:
Amortized cost	46,800	129,427
Unrealized gains	434	828
Unrealized losses	(6,682)	(7,449)
Fair value	40,552	122,806
Trading securities:
Fair value	29,701	29,541
Equity method securities
Equity method securities	217,380	26,775
Sponsored privately offered funds
Available for sale securities:
Amortized cost	500	265
Unrealized gains	325	305
Fair value	825	570
Equity method securities
Equity method securities	3,173	3,234
Total investment securities	4,000	3,800
Mortgage-backed securities
Trading securities:
Fair value	20	13
Corporate bonds
Trading securities:
Fair value	5
Common Stock
Trading securities:
Fair value	$ 87	101
Consolidated Sponsored Funds
Trading securities:
Fair value		$ 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 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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Amount after tax of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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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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Payments for investments classified as available for sale to equity method securities

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