INCOME TAXES - UNRECOGNIZED TAX BENEFITS (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance, beginning of year	$ 1,495,000	$ 1,800,000	$ 1,977,000
Additions based on tax related to the current year	259,000	268,000	109,000
Additions for tax positions of prior years			15,000
Reductions for tax positions of prior years	(42,000)	(90,000)
Reductions due to the statute of limitations	(800,000)	(340,000)	(301,000)
Settlements		(143,000)
Balance, end of year	912,000	1,495,000	1,800,000
Amount of unrecognized tax benefits that, if recognized, would favorably affect the effective income tax rate in future periods	721,000
Amount of interest and penalties
Interest and penalties recorded in the income statement	(258,000)	(290,000)	19,000
Interest and penalties accrued	$ 299,000	$ 557,000	$ 847,000