INCOME TAXES - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets
Stock-based compensation	$ 2,528	$ 2,130
Net operating loss and tax credit carryforwards	54,210	57,590
Interest expense limitation	7,344	7,344
Pension obligation	10,778	14,297
Excess and obsolete inventory	3,325	3,722
Accrued restructuring	2,223	2,468
Deferred revenue	4,195	3,048
Employee bonuses and commissions	3,861	5,388
Amortization	26,358	28,786
Operating lease liabilities	19,405	20,267
Other	8,017	8,925
Deferred tax assets	142,244	153,965
Less: Valuation allowance	(42,051)	(46,702)
Net deferred tax assets	100,193	107,263
Deferred tax liabilities
Depreciation and amortization	37,515	40,266
Unremitted earnings	4,435	4,173
Operating lease right-of-use assets	17,558	18,731
Other	3,364	3,380
Deferred tax liabilities	62,872	66,550
Net deferred tax assets	37,321	40,713
Deferred income tax assets	47,242	50,801
Deferred income tax liabilities	$ 9,921	$ 10,088