COMMITMENTS, CONTINGENCIES AND REGULATORY MATTERS - Leases (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Jan. 01, 2019
Lessee, Lease, Description [Line Items]
Right-to-use assets	$ 22,843		$ 22,843		$ 29,074	$ 42,100
Lease obligation liabilities						45,500
Lease obligation liabilities, current	9,300		9,300		11,398	16,700
Lease obligation liabilities, noncurrent	15,024		15,024		$ 19,707	28,800
Reduction in reduced accrued rent and lease incentives						$ 3,400
Sublease income	$ 400	$ 500	$ 700	$ 800
Minimum
Lessee, Lease, Description [Line Items]
Lease term	1 year		1 year
Maximum
Lessee, Lease, Description [Line Items]
Lease term	6 years		6 years