SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Activity in Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at beginning of period	$ 5,784	$ 2,019	$ 3,425
Charged to expense	2,983	3,985	6
Write-offs, net of recoveries	(387)	(220)	(1,412)
Balance at end of period	$ 8,380	$ 5,784	$ 2,019