ACQUISITIONS - Acquisition and Integration Expense (Details) - Acquisition and Integration Costs - All Current Acquirees - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Combination, Separately Recognized Transactions [Line Items]
Legal and professional fees	$ 528	$ 3,059	$ 1,033
Financial advisory fees	0	5,087	0
Facilities consolidation and discontinuation	0	1,323	488
Other	0	653	219
Total	$ 528	$ 10,122	$ 1,740