COMMITMENTS, CONTINGENCIES AND REGULATORY MATTERS - Lease Activity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Lessee, Lease, Description [Line Items]
Cash used in operating activities for amounts included in the measurement of lease liabilities	$ 2,375	$ 3,447	$ 5,453	$ 6,758
Short-term (twelve months or less) lease costs	(940)	1,222	(459)	2,427
Selling, general and administrative expense
Lessee, Lease, Description [Line Items]
Operating lease costs	1,118	2,529	3,210	4,810
Cost of revenue
Lessee, Lease, Description [Line Items]
Operating lease costs	$ 1,327	$ 635	$ 1,498	$ 1,269