SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Recently issued accounting pronouncements (Details) $ in Thousands		3 Months Ended
	Jan. 01, 2019 USD ($)	Mar. 31, 2019 USD ($) lease	Jun. 30, 2019 USD ($)
New accounting pronouncements
Lease, Practical Expedients, Package	true
Lease liability			$ 2,482
Operating lease right-of-use assets			$ 2,216
Number of lease agreements entered into during the period | lease		2
Increase in lease liability upon entering into new lease agreements		$ 900
Increase in right-of-use assets upon entering into new lease agreements		$ 900
ASU 2016-02 | Adjustment
New accounting pronouncements
Lease liability	$ 1,800
Operating lease right-of-use assets	$ 1,500