ACCUMULATED OTHER COMPREHENSIVE INCOME - Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net foreign currency translation adjustment	$ 12,829,000	$ (891,000)	$ (2,982,000)
Unrealized loss on cash flow hedge	(3,094,000)	(1,771,000)	0
Tax	809,000	372,000	0
Net of tax	(2,285,000)	(1,399,000)	0
Net change in postretirement benefit plan (see Note 15 for further information)
Prior service (credit)/cost and (gain)/loss arising during the period	(503,000)	199,000	522,000
Amortization of prior service credit/(cost)	74,000	74,000	74,000
Amortization of gain/(loss)	(50,000)	(46,000)	(8,000)
Total before tax	(479,000)	227,000	588,000
Tax	127,000	101,000	434,000
Adjustment	(455,000)	0	0
Net of tax	(807,000)	328,000	1,022,000
Other comprehensive gain/(loss)	9,737,000	(1,962,000)	(1,960,000)
Taxes on net investment hedge	$ 1,579,000	$ 70,000	$ 0