ACQUISITIONS - Acquisition and Integration Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Combination, Separately Recognized Transactions [Line Items]
Total	$ 22,635	$ 19,646	$ 7,718
Acquisition and Integration Costs | All Current Acquirees
Business Combination, Separately Recognized Transactions [Line Items]
Legal and professional fees	1,033	6,931	5,113
Financial advisory fees	0	0	2,413
Employee costs including redundant salaries and benefits and severance	0	2,016	3,554
Facilities consolidation and discontinuation	488	1,401	1,621
Bad debt expense and contractual adjustments related to acquired accounts receivable	0	5,430	0
Legal settlement	0	334	2,300
Other	219	1,812	1,129
Total	$ 1,740	$ 17,924	$ 16,130