NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Restricted Cash and Accounts Receivable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Rollforward of the allowance for doubtful accounts
Balance at beginning of period	$ 4,246	$ 3,379	$ 3,091
Charged to expense	1,292	2,186	1,802
Net write-offs	(1,043)	(1,319)	(1,514)
Balance at end of period	4,495	4,246	$ 3,379
Newport
Acquisitions
Restricted cash classified as noncurrent	$ 3,700
Adjustments for New Accounting Principle, Early Adoption
Acquisitions
Reclassification of deferred tax assets and liabilities		$ 6,700