COMMITMENTS, CONTINGENCIES AND REGULATORY MATTERS - Leases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Jan. 01, 2019
Lessee, Lease, Description [Line Items]
Right-to-use assets	$ 26,064		$ 29,074	$ 42,100
Lease obligation liabilities				45,500
Sublease income	$ 300	$ 400
Reduction in reduced accrued rent and lease incentives				$ 3,400
Minimum
Lessee, Lease, Description [Line Items]
Lease term	1 year
Maximum
Lessee, Lease, Description [Line Items]
Lease term	6 years