FAIR VALUE MEASUREMENTS - Fair Value of Assets and Liabilities Measured on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net liabilities	$ 0	$ 429
Net investment hedge
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net liabilities	(3,999)	(3,904)
Quoted Prices in Active Markets for Identical Items (Level 1) | Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net liabilities	0	0
Quoted Prices in Active Markets for Identical Items (Level 1) | Net investment hedge
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net liabilities	0	0
Significant Other Observable Inputs (Level 2) | Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net liabilities	0	0
Significant Other Observable Inputs (Level 2) | Net investment hedge
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net liabilities	(3,999)	(3,904)
Significant Unobservable Inputs (Level 3) | Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net liabilities	0	429
Significant Unobservable Inputs (Level 3) | Net investment hedge
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net liabilities	$ 0	$ 0