SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Recently issued accounting pronouncements (Details) $ in Thousands		3 Months Ended
	Jan. 01, 2019 USD ($)	Mar. 31, 2019 USD ($) lease	Sep. 30, 2019 USD ($)
New accounting pronouncements
Lease liability			$ 2,337
Operating lease right-of-use assets			$ 2,086
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
New accounting pronouncements
Change in Accounting Principle, Accounting Standards Update, Adopted	true
Change in Accounting Principle, Accounting Standards Update, Transition Option Elected	Modified Retrospective
New Accounting Pronouncement or Change in Accounting Principle, Prior Period Not Restated	true
Lease, Practical Expedients, Package	true
ASU 2016-02 | Adjustment
New accounting pronouncements
Lease liability	$ 1,800
Operating lease right-of-use assets	$ 1,500