Investment Securities - Investment securities and summary of the gains (losses) related to securities (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Available for sale securities:
Amortized cost	$ 89,778	$ 47,300
Unrealized gains	2,296	759
Unrealized losses	(6,259)	(6,682)
Fair value	85,815	41,377
Equity method securities	133,957	220,553
Trading securities:
Fair value	141,843	29,813
Investment securities	361,615	291,743
Equity method securities	133,957	220,553
Sponsored funds
Available for sale securities:
Amortized cost	89,278	46,800
Unrealized gains	1,928	434
Unrealized losses	(6,259)	(6,682)
Fair value	84,947	40,552
Equity method securities	130,898	217,380
Trading securities:
Fair value	29,924	29,701
Equity method securities	130,898	217,380
Sponsored privately offered funds measured at net asset value
Available for sale securities:
Amortized cost	500	500
Unrealized gains	368	325
Fair value	868	825
Equity method securities	3,059	3,173
Trading securities:
Equity method securities	3,059	3,173
Mortgage-backed securities
Trading securities:
Fair value	16	20
Corporate bonds
Trading securities:
Fair value	3	5
Common Stock
Trading securities:
Fair value	97	$ 87
Consolidated Sponsored Funds
Trading securities:
Fair value	$ 111,803

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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