SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Fair Value of Financial Instruments (Details)	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Fair Value of Financial Instruments
Transfers of financial assets between Level 1 and Level 2			$ 0
Transfers of financial assets between Level 2 and Level 1			0
Transfers of financial assets into Level 3	$ 0
Transfers of financial assets out of Level 3	0
Liabilities:
Contingent consideration	3,698,000	$ 6,073,000	1,703,000	$ 3,698,000
Change in the contingent consideration liability
Beginning Balance	3,698,000	6,073,000
Payment of contingent consideration	(2,401,000)	(3,386,000)
Change in value of contingent consideration	356,000	145,000
Accretion of contingent consideration	52,000	826,000
Unrealized (loss) gain related to currency translation	(2,000)	40,000
Ending Balance	1,703,000	3,698,000
Outstanding borrowings			99,113,000	116,700,000
Fair value of outstanding borrowing			$ 98,900,000	116,500,000
Debt instrument, valuation technique, extensible list			us-gaap:ValuationTechniqueDiscountedCashFlowMember
Debt instrument, measurement input, extensible list			us-gaap:MeasurementInputDiscountRateMember
Minimum
Liabilities:
Contingent consideration, measurement input			0.145
Change in the contingent consideration liability
Debt instrument, measurement input			0.053
Maximum
Liabilities:
Contingent consideration, measurement input			0.285
Change in the contingent consideration liability
Debt instrument, measurement input			0.055
Level 3
Liabilities:
Contingent consideration, valuation technique extensible list			us-gaap:IncomeApproachValuationTechniqueMember
Contingent consideration, measurement input Contingent consideration, measurement input			us-gaap:MeasurementInputDiscountRateMember
Recurring
Assets:
Cash equivalents			$ 315,000	303,000
Total			315,000	303,000
Liabilities:
Contingent consideration	3,698,000	3,698,000	1,703,000	3,698,000
Total			1,703,000	3,698,000
Change in the contingent consideration liability
Beginning Balance	3,698,000
Ending Balance	1,703,000	3,698,000
Recurring | Level 1
Assets:
Cash equivalents			315,000	303,000
Total			315,000	303,000
Recurring | Level 3
Liabilities:
Contingent consideration	3,698,000	3,698,000	1,703,000	3,698,000
Total			$ 1,703,000	$ 3,698,000
Change in the contingent consideration liability
Beginning Balance	3,698,000
Ending Balance	$ 1,703,000	$ 3,698,000