SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Fair Value (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($) item	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Liabilities:
Contingent consideration	$ 1,703	$ 3,698	$ 1,703
Change in the contingent consideration liability
Beginning Balance	1,703	3,698
Payment of contingent consideration	(1,730)	(2,401)
Change in value of contingent consideration		362
Accretion of contingent consideration	30	44
Unrealized (loss) gain related to currency translation	(3)	1
Ending Balance		$ 1,704
Outstanding borrowings	96,400		99,100
Fair value of outstanding borrowing	$ 96,300		98,900
Minimum
Change in the contingent consideration liability
Incremental borrowing rate used to discount future cash flows from financial instruments (as a percent)	5.27%
Maximum
Change in the contingent consideration liability
Incremental borrowing rate used to discount future cash flows from financial instruments (as a percent)	5.34%
Discount rate | Minimum
Liabilities:
Contingent consideration, measurement input | item	0.145
Discount rate | Maximum
Liabilities:
Contingent consideration, measurement input | item	0.285
Recurring
Assets:
Cash equivalents	$ 17		315
Total	17		315
Liabilities:
Contingent Consideration Classified as Equity, Fair Value Disclosure			1,703
Total			1,703
Recurring | Level1
Assets:
Cash equivalents	17		315
Total	$ 17		315
Recurring | Level3
Liabilities:
Contingent Consideration Classified as Equity, Fair Value Disclosure			1,703
Total			$ 1,703