Consolidation - Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Noncontrolling interests	$ (131,669)	$ (131,525)	$ (115,513)	$ (99,277)	$ (90,687)	$ (63,845)
VOEs
Variable Interest Entity [Line Items]
Cash and cash equivalents	785		9,837
Investments	24,902		57,256
Other assets	4		1,989
Notes payable	0		0
Securities purchased payable and other liabilities	(648)		(2,566)
Noncontrolling interests	(6,487)		(24,707)
Net interests in CIP	18,556		41,809
CLOs
Variable Interest Entity [Line Items]
Cash and cash equivalents	153,825		82,295
Investments	2,085,625		2,217,055
Other assets	26,006		10,484
Notes payable	(2,083,827)		(2,190,445)
Securities purchased payable and other liabilities	(103,035)		(42,940)
Noncontrolling interests	(8,813)		(9,799)
Net interests in CIP	69,781		66,650
Other
Variable Interest Entity [Line Items]
Cash and cash equivalents	1,638		1,206
Investments	62,746		58,966
Other assets	819		957
Notes payable	0		0
Securities purchased payable and other liabilities	(1,007)		(323)
Noncontrolling interests	(6,321)		(3,354)
Net interests in CIP	$ 57,875		$ 57,452