SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Restructuring Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Restructuring Reserve [Roll Forward]
Charged to restructuring costs	$ 564	$ 1,140
Restructuring costs	564	$ 1,140
Employee Termination Costs | 2019 Restructuring Plan
Restructuring Reserve [Roll Forward]
Beginning balance	386
Charged to restructuring costs	212
Payments	(292)
Ending balance	306
Restructuring costs	212
Lease-Related Exit Costs | 2019 Restructuring Plan
Restructuring Reserve [Roll Forward]
Beginning balance	1,223
Charged to restructuring costs	0
Payments	(56)
Ending balance	1,167
Restructuring costs	0
Legal Entity Reorganization
Restructuring Reserve [Roll Forward]
Charged to restructuring costs	200
Restructuring costs	200
Strategic Reduction of Real Estate Footprint
Restructuring Reserve [Roll Forward]
Charged to restructuring costs	200
Restructuring costs	$ 200