RESTRUCTURING COSTS AND ACCRUALS (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring Costs									$ 629	$ 5,148	$ 7,059
Restructuring and Related Cost, Incurred Cost									604	3,537	5,084
Other Restructuring Costs									25	1,611	1,975
Restructuring accrual [Roll Forward]
Restructuring charges	$ 113	$ 229	$ (269)	$ 558	$ 1,747	$ 226	$ 268	$ 2,907	629	5,148	7,059
Facilties-related accuals - noncurrent	0				188				0	188
Fixed asset write-off									0	1,083	3,191
Accrual Adjustment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost									599	3,537	5,084
Restructuring accrual [Roll Forward]
Accrual balance at beginning of year				2,859				4,477	2,859	4,477	9,534
Accretion									0	103	325
Payments for Restructuring									(2,964)	(5,258)	(10,548)
Foreign exchange impact on ending balance									(21)	0	82
Accrual balance at end of year	155				2,859				155	2,859	4,477
Facilities-related accruals - current	155								155
Facilties-related accuals - noncurrent	0								0
Effectof842onRestructuring									(318)
Employee-Related [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Costs									599	3,641	2,145
Restructuring and Related Cost, Incurred Cost									599	3,641	2,145
Restructuring accrual [Roll Forward]
Accrual balance at beginning of year				2,541				1,998	2,541	1,998	6,226
Accretion									0	0	0
Payments for Restructuring									(2,964)	(3,099)	(6,439)
Foreign exchange impact on ending balance									(21)	1	66
Accrual balance at end of year	155				2,541				155	2,541	1,998
Restructuring charges										3,600
Facilities-related accruals - current	155								155
Facilties-related accuals - noncurrent	0								0
Effectof842onRestructuring									0
Facilities-Related [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Costs									5	(104)	2,939
Restructuring and Related Cost, Incurred Cost									0	(104)	2,939
Restructuring accrual [Roll Forward]
Accrual balance at beginning of year				$ 318				$ 2,479	318	2,479	3,308
Accretion									0	103	325
Payments for Restructuring									0	(2,159)	(4,109)
Foreign exchange impact on ending balance									0	(1)	16
Accrual balance at end of year	0				318				0	318	2,479
Facilities-related accruals - current	0				100				0	100
Facilties-related accuals - noncurrent	$ 0				$ 200				0	$ 200
Effectof842onRestructuring									$ (318)
2016 Plan [Member]
Restructuring accrual [Roll Forward]
Revisions of estimated liabilities											1,100
Restructuring charges											3,100
2016 Plan [Member] | Employee-Related [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Costs											$ 7,100
Restructuring accrual [Roll Forward]
Number of positions eliminated									54	84	102
2016 Plan [Member] | Facilities-Related [Member]
Restructuring accrual [Roll Forward]
Restructuring charges											$ 5,100
Fixed asset write-off										$ 1,100	$ 3,200