RESTRUCTURING COSTS AND ACCRUALS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	$ (16)	$ (402)	$ (1,911)	$ (4,589)
Other Restructuring Costs	(242)	(180)	(1,490)	(1,875)
Restructuring accrual [Roll Forward]
New restructuring charges - operating expenses	(226)	582	(3,401)	(6,464)
Accretion			101
Cash payments			(4,626)
Foreign exchange impact on ending balance			6
Facilities-related accruals - current	1,651		1,651
Facilities-related accruals - non-current	218		218		$ 731
Restructuring Charges	226	(582)	3,401	6,464
Employee Severance [Member]
Restructuring accrual [Roll Forward]
Accrual balance at beginning of year			1,998
New restructuring charges - operating expenses	(879)	(1,137)	(1,734)	(1,225)
Accretion			0
Cash payments			(2,369)
Foreign exchange impact on ending balance			5
Accrual balance at end of period	1,368		1,368
Facilities-related accruals - current	1,368		1,368
Facilities-related accruals - non-current	0		0
Employee Severance [Member] | Acquisition-Related [Member]
Restructuring accrual [Roll Forward]
Accrual balance at beginning of year			4,477
Accrual balance at end of period	1,869		1,869
Facilities-Related [Member]
Restructuring accrual [Roll Forward]
Accrual balance at beginning of year			2,479
New restructuring charges - operating expenses	(895)	(735)	(177)	(3,364)
Revisions of estimated liabilities			200
Non-cash write-offs				3,200
Accretion			101
Cash payments			(2,257)
Foreign exchange impact on ending balance			1
Accrual balance at end of period	501		501
Facilities-related accruals - current	283		283
Facilities-related accruals - non-current	218		218
2016 Plan [Member]
Restructuring accrual [Roll Forward]
Revisions of estimated liabilities		$ 600
Restructuring Charges	200		3,400	6,500
2016 Plan [Member] | Employee Severance [Member]
Restructuring accrual [Roll Forward]
Restructuring Charges			1,700	1,200
2016 Plan [Member] | Facilities-Related [Member]
Restructuring accrual [Roll Forward]
Restructuring Charges				$ 5,200
Accrued Expenses and Other Current Liabilities [Member] | Facilities-Related [Member]
Restructuring accrual [Roll Forward]
Facilities-related accruals - current	300		300
Other Noncurrent Liabilities [Member] | Facilities-Related [Member]
Restructuring accrual [Roll Forward]
Facilities-related accruals - non-current	200		200
Property, Plant and Equipment [Member] | Facilities-Related [Member]
Restructuring accrual [Roll Forward]
Facilities-related accruals - non-current	$ 1,100		$ 1,100