INCOME TAXES - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of beginning and ending balances of unrecognized tax benefits
Unrecognized tax benefits, at beginning of the year	$ 4,860	$ 4,664	$ 7,567	$ 7,605
Additions for tax positions related to the current year		196	47	279
Additions for tax positions of prior years				1,415
Decrease related to prior year positions				(1,472)
Decrease for lapse of applicable statute of limitations			(2,950)	(260)
Unrecognized tax benefits, at end of the year		4,860	4,664	7,567
Total amount of unrecognized tax benefits, if recognized, would affect the effective tax rate		2,900
Accrued interest and penalties		$ 600	$ 400	$ 500
Corporate federal income tax rate (as a percent)		35.00%	35.00%	35.00%
Provisional amount for tax expense, in accordance with Staff Accounting Bulletin 118		$ 35,000
Forecast
Reconciliation of beginning and ending balances of unrecognized tax benefits
Corporate federal income tax rate (as a percent)	21.00%