SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Summary of Changes in Allowance for Doubtful Accounts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Changes in allowance for doubtful accounts against accounts receivables:
Balance at the beginning of the period	$ 4,406	$ 7,619	$ 7,390
Provision for doubtful accounts	5,664	4,030	1,404
Write-offs	(2,271)	(7,243)	(1,175)
Balance at the end of the period	$ 7,799	$ 4,406	$ 7,619