FAIR VALUE MEASUREMENTS - Acquisition-related Contingent Consideration (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Increase from revaluation of contingent consideration	$ (885)	$ (772)
Recurring basis | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balance at January 1, 2017	87,478
Increase from revaluation of contingent consideration	11,057
Contractual payments included in accrued liabilities at September 30, 2017	(1,993)
Contractual payments	(3,782)
Foreign currency impact	155
Balance at September 30, 2017	$ 92,915