GOODWILL AND INTANGIBLE ASSETS - Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2021	Dec. 31, 2020
Goodwill [Roll Forward]
Goodwill, beginning balance		$ 371,047	$ 143,855
Acquisitions		417,753	224,601
Foreign currency translation		(828)	2,591
Goodwill, ending balance		787,972	371,047
Credit Group
Goodwill [Roll Forward]
Goodwill, beginning balance		32,196	32,196
Acquisitions		0	0
Foreign currency translation		0	0
Goodwill, ending balance		32,196	32,196
Private Equity Group
Goodwill [Roll Forward]
Goodwill, beginning balance		58,600	58,600
Acquisitions		0	0
Foreign currency translation		0	0
Goodwill, ending balance		58,600	58,600
Real Estate Group
Goodwill [Roll Forward]
Goodwill, beginning balance		53,120	53,059
Acquisitions		0	0
Foreign currency translation		219	61
Goodwill, ending balance		53,339	53,120
Secondary Solutions Group
Goodwill [Roll Forward]
Goodwill, beginning balance		0	0
Acquisitions		417,753	0
Foreign currency translation		(15)	0
Goodwill, ending balance		417,738	0
Strategic Initiatives
Goodwill [Roll Forward]
Goodwill, beginning balance		227,131	0
Acquisitions	$ 224,600	0	224,601
Foreign currency translation		(1,032)	2,530
Goodwill, ending balance		$ 226,099	$ 227,131