Consolidation - Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Noncontrolling interests	$ (90,687)	$ (87,115)	$ (63,845)	$ (60,502)	$ (59,003)	$ (57,481)
VOEs
Variable Interest Entity [Line Items]
Cash and cash equivalents	9,966		2,665
Investments	45,560		22,223
Other assets	5,328		1,563
Notes payable	0		0
Securities purchased payable and other liabilities	(5,250)		(2,964)
Noncontrolling interests	(22,304)		(3,865)
Net interests in CIP	33,300		19,622
CLOs
Variable Interest Entity [Line Items]
Cash and cash equivalents	72,721		97,130
Investments	2,194,211		1,976,148
Other assets	23,894		21,450
Notes payable	(2,156,587)		(1,834,535)
Securities purchased payable and other liabilities	(66,707)		(164,887)
Noncontrolling interests	(8,345)		(10,558)
Net interests in CIP	59,187		84,748
Other
Variable Interest Entity [Line Items]
Cash and cash equivalents	1,098		363
Investments	34,049		31,739
Other assets	565		599
Notes payable	0		0
Securities purchased payable and other liabilities	(356)		(200)
Noncontrolling interests	(2,041)		(1,564)
Net interests in CIP	$ 33,315		$ 30,937