PROPERTY AND EQUIPMENT - Schedule of property and equipment, net (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total gross property and equipment	$ 82,619	$ 49,342
Accumulated depreciation	(20,238)	(17,979)
Total property and equipment, net	62,381	31,363
Computer equipment and capitalized software
Property, Plant and Equipment [Line Items]
Total gross property and equipment	34,777	28,425
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total gross property and equipment	5,012	7,751
Furniture and other equipment
Property, Plant and Equipment [Line Items]
Total gross property and equipment	3,290	3,993
Aircraft and automobile
Property, Plant and Equipment [Line Items]
Total gross property and equipment	2,621	2,621
Projects in progress
Property, Plant and Equipment [Line Items]
Total gross property and equipment	$ 36,919	$ 6,552