Consolidation - Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Noncontrolling interests	$ (87,115)	$ (63,845)	$ (59,003)	$ (57,481)
VOEs
Variable Interest Entity [Line Items]
Cash and cash equivalents	11,790	2,665
Investments	44,525	22,223
Other assets	6,485	1,563
Notes payable	0	0
Securities purchased payable and other liabilities	(8,419)	(2,964)
Noncontrolling interests	(23,540)	(3,865)
Net interests in CIP	30,841	19,622
CLOs
Variable Interest Entity [Line Items]
Cash and cash equivalents	221,505	97,130
Investments	2,117,938	1,976,148
Other assets	22,532	21,450
Notes payable	(2,134,108)	(1,834,535)
Securities purchased payable and other liabilities	(138,977)	(164,887)
Noncontrolling interests	(10,247)	(10,558)
Net interests in CIP	78,643	84,748
Other
Variable Interest Entity [Line Items]
Cash and cash equivalents	1,875	363
Investments	27,294	31,739
Other assets	416	599
Notes payable	0	0
Securities purchased payable and other liabilities	(438)	(200)
Noncontrolling interests	(1,406)	(1,564)
Net interests in CIP	$ 27,741	$ 30,937