SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated other comprehensive income (loss)
Beginning Balance	$ 676,122
Unrecognized actuarial gain (loss), net of tax of $0.1, $0.1 and $0.6 million for the years December 31, 2020, 2019 and 2018 respectively	(2,412)	$ (445)	$ (840)
Foreign currency translation adjustment	37	(1,041)	(4,390)
Interest rate swap	(101)	(187)	78
Reclassification of foreign currency losses on assets held for sale	6,036
Ending Balance	645,649	676,122
Adjust funded status of pension plan, tax	100	100	600
Accumulated Other Comprehensive Income/(Loss)
Accumulated other comprehensive income (loss)
Beginning Balance	(3,282)	(1,609)	3,746
Unrecognized actuarial gain (loss), net of tax of $0.1, $0.1 and $0.6 million for the years December 31, 2020, 2019 and 2018 respectively	(2,412)	(445)	(840)
Foreign currency translation adjustment	37	(1,041)	(4,390)
Interest rate swap	(101)	(187)	78
Reclassification of foreign currency losses on assets held for sale	6,036
Ending Balance	278	(3,282)	(1,609)
Pension and Postretirement benefit plans
Accumulated other comprehensive income (loss)
Beginning Balance	1,842	2,287	3,127
Unrecognized actuarial gain (loss), net of tax of $0.1, $0.1 and $0.6 million for the years December 31, 2020, 2019 and 2018 respectively	(2,412)	(445)	(840)
Ending Balance	(570)	1,842	2,287
Translation Adjustment
Accumulated other comprehensive income (loss)
Beginning Balance	(5,076)	(4,035)	355
Foreign currency translation adjustment	37	(1,041)	(4,390)
Ending Balance	(5,039)	(5,076)	(4,035)
Other
Accumulated other comprehensive income (loss)
Beginning Balance	(48)	139	264
Interest rate swap	(101)	(187)	78
Reclassification of foreign currency losses on assets held for sale	6,036
Ending Balance	$ 5,887	$ (48)	139
Cumulative Effect, Period of Adoption, Adjustment | Accumulated Other Comprehensive Income/(Loss)
Accumulated other comprehensive income (loss)
Beginning Balance			(203)
Cumulative Effect, Period of Adoption, Adjustment | Other
Accumulated other comprehensive income (loss)
Beginning Balance			$ (203)