RESTRUCTURING COSTS AND ACCRUALS (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Restructuring accrual [Roll Forward]
Accrual balance at beginning of year				$ 10,111				$ 7,180	$ 10,111	$ 7,180	$ 2,343
New restructuring charges									4,621	11,434	5,766
Revisions of estimated liabilities									(753)	266	539
Accretion									325	287	226
Cash payments									(11,002)	(9,926)	(1,616)
Non-cash write-offs									3,191	1,137
Foreign exchange impact on ending balance									(49)	(267)	(78)
Accrual balance at end of year	$ 6,444				$ 10,111				6,444	10,111	7,180
Restructuring charges	595	$ (582)	$ 6,063	983	4,959	$ 5,314	$ (213)	2,777	7,059	12,837	6,305
Facilties-related accuals - noncurrent	731				1,256				731	1,256
Fixed asset write-off									3,191	1,137	0
Facilities-Related and Other [Member]
Restructuring accrual [Roll Forward]
Accrual balance at beginning of year				3,093				1,671	3,093	1,671	2,285
New restructuring charges									1,526	943	0
Revisions of estimated liabilities									334	763	539
Accretion									325	287	226
Cash payments									(4,252)	(1,701)	(1,301)
Non-cash write-offs									3,191	1,137
Foreign exchange impact on ending balance									16	(7)	(78)
Accrual balance at end of year	4,233				3,093				4,233	3,093	1,671
Employee-Related [Member]
Restructuring accrual [Roll Forward]
Accrual balance at beginning of year				$ 7,018				$ 5,509	7,018	5,509	58
New restructuring charges									3,095	10,491	5,766
Revisions of estimated liabilities									(1,087)	(497)	0
Accretion									0	0	0
Cash payments									(6,750)	(8,225)	(315)
Non-cash write-offs									0	0
Foreign exchange impact on ending balance									(65)	(260)	0
Accrual balance at end of year	2,211				7,018				2,211	7,018	$ 5,509
Facilities-Related [Member]
Restructuring accrual [Roll Forward]
Accrual balance at end of year	2,500								2,500
Facilities-related accruals - current	300				700				300	700
Facilties-related accuals - noncurrent	700				1,300				700	1,300
2016 Plan [Member]
Restructuring accrual [Roll Forward]
Revisions of estimated liabilities										10,000
2016 Plan [Member] | Employee-Related [Member]
Restructuring accrual [Roll Forward]
Restructuring charges	$ 600				$ 5,000				$ 7,100	$ 12,800
Number of positions eliminated									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
Restructuring Plan 2012 [Member] | Facilities-Related [Member]
Restructuring accrual [Roll Forward]
Revisions of estimated liabilities		$ 800