NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Restricted Cash and Accounts Receivable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Restricted cash classified as noncurrent		$ 3,700
Rollforward of the allowance for doubtful accounts
Balance at beginning of period	$ 4,495	4,246	$ 3,379
Charged to expense	1,974	1,292	2,186
Net write-offs	(4,345)	(1,043)	(1,319)
Balance at end of period	$ 2,124	$ 4,495	$ 4,246