INCOME TAXES - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current:
United States-Federal									$ 504	$ (1,559)	$ 24,546
United States-State									3	(336)	4,506
Foreign									7,611	8,192	13,060
Total current income tax expense									8,118	6,297	42,112
Deferred:
United States-Federal									(6,527)	(1,805)	(17,947)
United States-State									(413)	(93)	(2,832)
Foreign									(377)	(294)	(2,463)
Total deferred income tax expense (benefit)									(7,317)	(2,192)	(23,242)
Consolidated:
United States-Federal									(6,023)	(3,364)	6,599
United States-State									(410)	(429)	1,674
Foreign									7,234	7,898	10,597
Total income tax expense (benefit)	$ 1,858	$ 92	$ (2,258)	$ 1,109	$ 1,332	$ 1,834	$ (274)	$ 1,213	801	4,105	$ 18,870
Deferred tax assets:
Accounts receivable and inventory allowances	1,972				1,603				1,972	1,603
Basis in investments	7,512				6,937				7,512	6,937
Accrued expenses	4,701				5,923				4,701	5,923
Deferred revenue	3,141				2,864				3,141	2,864
Employee benefits	4,363				3,559				4,363	3,559
Other, net	744								744
Net operating losses	26,582				40,491				26,582	40,491
Tax Credits	1,997				2,726				1,997	2,726
Operating lease liability	14,648				15,869				14,648	15,869
Total deferred tax asset	65,660				79,972				65,660	79,972
Deferred tax liabilities:
Acquired intangible assets, property and equipment	26,736				30,419				26,736	30,419
Right-of-use asset	14,594				15,869				14,594	15,869
Prepaid expense	209				181				209	181
Other, net					195					195
Total deferred tax liabilities	41,539				46,664				41,539	46,664
Valuation allowance	(31,014)				(39,406)				(31,014)	(39,406)
Net deferred tax liabilities	(6,893)				(6,098)				(6,893)	(6,098)
Deferred tax assets:
Total deferred tax asset	3,782				2,582				3,782	2,582
Deferred tax liabilities:
Total deferred tax liabilities	(10,675)				(8,680)				(10,675)	(8,680)
Net deferred tax liabilities	$ (6,893)				$ (6,098)				$ (6,893)	$ (6,098)