LEASES (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) item	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) item	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Nov. 15, 2018
Leases
Restricted cash	$ 12,584	$ 12,578	$ 12,584	$ 12,578	$ 12,582
Variable lease cost	$ 658	383	$ 1,068	507
Remaining lease term			1 year 8 months 12 days
Number of vehicles leased under a master fleet lease agreement | item	65		65
Term of vehicle lease			3 years
Amount borrowed	$ 500		$ 500
Lease cost
Operating lease cost	1,185	1,187	2,371	2,243
Variable Lease, Cost	658	383	1,068	507
Total lease cost	1,843	1,570	3,439	2,750
Operating cash outflows from operating leases	1,686	$ 911	3,130	1,654
Operating Lease, Right-of-Use Asset	$ 28,829		$ 28,829		$ 29,781
Watertown Lease
Leases
Lease term	13 years		13 years
Restricted cash	$ 2,000		$ 2,000
Discount rate (as a percent)						9.90%
Variable lease cost			$ 1,100	500
Remaining lease term			11 years 3 months 18 days
Lease cost
Variable Lease, Cost			$ 1,100	$ 500