FAIR VALUE MEASUREMENT OF FINANCIAL INSTRUMENTS - Significant Unobservable Inputs for Contingent Consideration (Details) - (Level 3) $ in Thousands	Jun. 30, 2019 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of contingent consideration	$ 9,555
Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration inputs under Monte Carlo simulation	0.110
Revenue volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration inputs under Monte Carlo simulation	0.130
Risk free rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration inputs under Monte Carlo simulation	0.020