INCOME TAXES - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits, Beginning Balance	$ 14,210	$ 11,189	$ 17,530
Additions based on tax positions related to the current year	1,309	2,936	2,378
Additions for tax positions of prior years		1,484
Reductions based on tax positions related to the current year			(6,589)
Reductions for tax positions of prior years	(2,733)	(99)	(345)
Lapse of statute of limitations	(4,416)	(1,300)	(1,785)
Unrecognized Tax Benefits, Ending Balance	$ 8,370	$ 14,210	$ 11,189