Consolidation - Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Noncontrolling interests	$ (59,003)	$ (57,481)	$ (4,162)	$ (4,178)
VOEs
Variable Interest Entity [Line Items]
Cash and cash equivalents	592	1,029
Investments	15,495	12,923
Other assets	66	228
Notes payable	0	0
Securities purchased payable and other liabilities	(482)	(823)
Noncontrolling interests	(4,645)	(2,348)
The Company’s net interests in consolidated investment products	11,026	11,009
CLOs
Variable Interest Entity [Line Items]
Cash and cash equivalents	54,805	51,363
Investments	1,723,411	1,709,266
Other assets	30,444	30,426
Notes payable	(1,640,360)	(1,620,260)
Securities purchased payable and other liabilities	(74,070)	(69,737)
Noncontrolling interests	(12,948)	(13,958)
The Company’s net interests in consolidated investment products	81,282	87,100
Other
Variable Interest Entity [Line Items]
Cash and cash equivalents	326	559
Investments	29,036	27,379
Other assets	643	403
Notes payable	0	0
Securities purchased payable and other liabilities	(390)	(146)
Noncontrolling interests	0	(36)
The Company’s net interests in consolidated investment products	$ 29,615	$ 28,159