COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended			36 Months Ended
	Jul. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Apr. 30, 2020	Feb. 01, 2018	Dec. 31, 2016
Loss Contingencies [Line Items]
Operating Leases, Income Statement, Sublease Revenue		$ 1,300	$ 1,200	$ 700
Operating Leases, Rent Expense, Net		10,300	9,500	11,800
Long-term Purchase Commitment, Amount					$ 10,700
Future minimum lease commitments under non-cancelable leases [Abstract]
Operating Leases, Future Minimum Payments Due, Next Twelve Months		9,804	11,225
Operating Leases, Future Minimum Payments, Due in Two Years		6,604	9,784
Operating Leases, Future Minimum Payments, Due in Three Years		5,712	6,850
Operating Leases, Future Minimum Payments, Due in Four Years		4,756	5,982
Operating Leases, Future Minimum Payments, Due in Five Years		4,638	4,754
Operating Leases, Future Minimum Payments, Due Thereafter		15,388	20,040
Total		$ 46,902	58,635
Purchase Commitments [Abstract]
Maximum Purchase Commitment Period (in Years)		1 year
Aggregate total of non-cancelable purchase commitments		$ 13,800
Product warranty accrual [Roll Forward]
Accrual balance at beginning of year		1,706	2,545	2,518
Accruals for product warranties		973	858	2,572
Cost of warranty claims		(1,342)	(1,697)	(2,545)
Accrual balance at end of period		1,337	1,706	2,545
Facilities-Related [Member]
Loss Contingencies [Line Items]
Restructuring Reserve		0	$ 318	$ 2,479			$ 3,308
Standby Letters of Credit [Member] | Office Space - Burlington, Massachusetts [Member]
Loss Contingencies [Line Items]
Letters of Credit Outstanding, Amount		1,300
Loss Contingency, Range Of Possible Loss, Portion Not Accrued, Minimum		1,200
Minimum exposure		1,200
Standby Letters of Credit [Member] | Office Space - Other Facilities [Member]
Loss Contingencies [Line Items]
Letters of Credit Outstanding, Amount		600
Standby Letters of Credit [Member] | Other Operating Obligations [Member]
Loss Contingencies [Line Items]
Letters of Credit Outstanding, Amount		1,600
Standby Letters of Credit [Member] | Purchase Order Obligations [Member]
Loss Contingencies [Line Items]
Letters of Credit Outstanding, Amount						$ 8,500
Increase (Decrease) in Restricted Cash	$ (8,500)
Operating Leases on Vacated Facilities [Member]
Loss Contingencies [Line Items]
Effect on Future Cash Flows, Amount		2,900
Aggregate obligation of vacated facilies		$ 2,900
Forecast [Member]
Loss Contingencies [Line Items]
Long-term Purchase Commitment, Amount					$ 12,800