SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Changes in AOCI (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Changes in Accumulated Other Comprehensive Income (Loss)
Beginning Balance	$ (750)	$ (418)
Other comprehensive loss before reclassifications	(1,610)	(11)
Amounts reclassified from accumulated other comprehensive loss	24	(2)
Net current period change in accumulated other comprehensive loss	(1,586)	(13)
Ending Balance	(2,336)	(431)
Cumulative Translation Adjustment
Changes in Accumulated Other Comprehensive Income (Loss)
Beginning Balance	(61)	(204)
Other comprehensive loss before reclassifications	20	(8)
Net current period change in accumulated other comprehensive loss	20	(8)
Ending Balance	(41)	(212)
Unrealized Gain (Loss) on Securities
Changes in Accumulated Other Comprehensive Income (Loss)
Beginning Balance	(689)	(214)
Other comprehensive loss before reclassifications	(1,630)	(3)
Amounts reclassified from accumulated other comprehensive loss	24	(2)
Net current period change in accumulated other comprehensive loss	(1,606)	(5)
Ending Balance	$ (2,295)	$ (219)