COMMITMENTS, CONTINGENCIES AND REGULATORY MATTERS - Lease Activity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Lessee, Lease, Description [Line Items]
Cash used in operating activities for amounts included in the measurement of lease liabilities	$ 3,496	$ 3,771	$ 10,254	$ 12,228
Short-term (twelve months or less) lease costs	699	1,539	3,126	3,848
Selling, general and administrative expense
Lessee, Lease, Description [Line Items]
Operating lease costs	2,566	1,752	7,376	8,368
Cost of revenue
Lessee, Lease, Description [Line Items]
Operating lease costs	$ 479	$ 567	$ 1,748	$ 2,279