SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Recently Adopted Accounting Standards (Details) - USD ($) $ in Thousands	Jan. 01, 2019	Mar. 31, 2019
Recently Adopted Accounting Standards
Operating lease liabilities		$ 5,624
Operating lease assets		$ 5,388
ASU 2016-02
Recently Adopted Accounting Standards
Lease, Practical Expedients, Package [true/false]	true
Lease, Practical Expedient, Use of Hindsight [true/false]	false
Operating lease liabilities	$ 5,731
Operating lease assets	$ 5,731