COMMITMENTS, CONTINGENCIES AND REGULATORY MATTERS - Lease Activity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Lessee, Lease, Description [Line Items]
Cash used in operating activities for amounts included in the measurement of lease liabilities	$ 1,690	$ 3,496	$ 7,143	$ 10,254
Short-term (twelve months or less) lease costs	(343)	699	(802)	3,126
Selling, general and administrative expense
Lessee, Lease, Description [Line Items]
Operating lease costs	1,486	2,566	4,696	7,376
Cost of revenue
Lessee, Lease, Description [Line Items]
Operating lease costs	$ 398	$ 479	$ 1,896	$ 1,748