RESTRUCTURING COSTS AND ACCRUALS (Details) $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring Costs	$ 1,700									$ 5,148	$ 7,059	$ 12,837
Restructuring and Related Cost, Incurred Cost										3,537	5,084	11,798
Other Restructuring Costs										1,611	1,975	1,039
Restructuring accrual [Roll Forward]
Accrual balance at beginning of year				$ 4,477				$ 9,534		4,477	9,534	6,346
Accretion										103	325	287
Payments for Restructuring										(5,258)	(10,548)	(8,693)
Foreign exchange impact on ending balance										0	82	(204)
Accrual balance at end of year	2,859				$ 4,477				$ 9,534	2,859	4,477	9,534
Restructuring charges	1,747	$ 226	$ 268	2,907	595	$ (582)	$ 6,063	983		5,148	7,059	12,837
Facilities-related accruals - current	2,671									2,671
Facilties-related accuals - noncurrent	188				731					188	731
Fixed asset write-off										1,083	3,191	1,137
Employee-Related [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Costs										3,641	2,145	8,740
Restructuring and Related Cost, Incurred Cost										3,641	2,145	8,740
Restructuring accrual [Roll Forward]
Accrual balance at beginning of year				1,998				6,226		1,998	6,226	4,675
Accretion										0	0	0
Payments for Restructuring										(3,099)	(6,439)	(6,992)
Foreign exchange impact on ending balance										1	66	(197)
Accrual balance at end of year	2,541				1,998				6,226	2,541	1,998	6,226
Facilities-related accruals - current	2,541									2,541
Facilties-related accuals - noncurrent	0									0
Facilities-Related [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Costs										(104)	2,939	3,058
Restructuring and Related Cost, Incurred Cost										(104)	2,939	3,058
Restructuring accrual [Roll Forward]
Accrual balance at beginning of year				$ 2,479				$ 3,308		2,479	3,308	1,671
Accretion										103	325	287
Payments for Restructuring										(2,159)	(4,109)	(1,701)
Foreign exchange impact on ending balance										(1)	16	(7)
Accrual balance at end of year	318				2,479				3,308	318	2,479	3,308
Facilities-related accruals - current	130									130
Facilties-related accuals - noncurrent	$ 188									$ 188
2016 Plan [Member]
Restructuring accrual [Roll Forward]
Revisions of estimated liabilities											1,100	10,000
Restructuring charges											3,100
2016 Plan [Member] | Employee-Related [Member]
Restructuring accrual [Roll Forward]
Restructuring charges					$ 600				$ 5,000		$ 7,100	$ 12,800
Number of positions eliminated										84	102	279
2016 Plan [Member] | Facilities-Related [Member]
Restructuring accrual [Roll Forward]
Restructuring charges											$ 5,100	$ 2,800
Fixed asset write-off										$ 1,100	$ 3,200	1,100
Restructuring Plan 2012 [Member] | Facilities-Related [Member]
Restructuring accrual [Roll Forward]
Revisions of estimated liabilities												$ 800