INCOME TAXES - Unrecognized tax benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes
Recognized tax benefit	$ 700
Accrued interest and penalties on unrecognized tax benefits	2,300	$ 3,000
Interest and penalties recorded on unrecognized tax benefits	(400)
Reconciliation of total amounts of unrecognized tax benefits
Balance at beginning of the period	1,047	999	$ 1,287
Gross increases - tax positions in prior period	301	48
Gross decreases - tax positions in prior period			(31)
Gross increases - tax positions in current period	128		45
Settlement			(103)
Lapse of statute of limitations			(199)
Balance at end of the period	1,476	$ 1,047	$ 999
Deferred taxes provided for withholding or other taxes for repatriation of foreign earnings	0
Undistributed earnings from foreign subsidiaries	109,700
Foreign withholding taxes on the undistributed earnings	$ 4,700