Investments Trading and Equity Investments (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2021 USD ($) security new_funds_seeded	Mar. 31, 2020 USD ($) new_funds_seeded	Dec. 31, 2020 USD ($)
Trading Securities and Other Trading Assets [Line Items]
Equity investments at fair value		$ 100,486		$ 94,089
Equity method investments		15		541
Trading		27,936		18,700
Held-to-maturity		0		41,648
Investments	[1]	$ 128,437		154,978
Debt securities, held-to-maturity, matured in period, amount				$ 41,700
Debt securities, held-to-maturity, number of securities matured | security		2
Debt securities, held-to-maturity, matured in the period		$ 25,000
Debt securities, held-to-maturity, number of securities sold | security		2
Debt securities, held-to-maturity, sold, amount		$ 16,700
Number of new funds seeded | new_funds_seeded		0	0
Gain (Loss) on Investments [Abstract]
Net realized gains (losses) during the period		$ 1,889	$ (1,230)
Net unrealized gains (losses) during the period on investments still held at the end of the period		2,670	(20,797)
Gain (loss) from investments—net		$ 4,559	$ (22,027)

[1] Asset and liability amounts in parentheses represent the aggregated balances at March 31, 2021 and December 31, 2020 attributable to variable interest entities consolidated by the Company. Refer to Note 4 for further discussion.