INCOME TAXES - Reconciliation of Unrecognized Tax Benefits, Excluding Interest and Penalties (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 of period	$ 12,268	$ 13,271	$ 18,274
Additions based on tax positions related to the current year	4,014	0	1,520
Additions for tax positions of prior years	16,713	55	0
Reductions for tax positions of prior years	0	(211)	(810)
Lapse in statute of limitations	(1,189)	(847)	(5,188)
Settlements	0	0	(525)
Unrecognized tax benefits, end of the period	$ 31,806	$ 12,268	$ 13,271