BALANCE SHEET COMPONENTS (Components of significant balance sheet accounts) (Details) - USD ($) $ in Thousands		Sep. 28, 2019	Sep. 29, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Short-term investments	[1]	$ 229,000	$ 293,000
Inventories, net:
Raw materials and supplies		52,853	63,894
Work in process		32,026	37,829
Finished goods		33,742	40,357
Inventory, gross		118,621	142,080
Inventory reserves		(29,313)	(26,889)
Inventories, net		89,308	115,191
Property, plant and equipment, net:
Land		2,182	2,182
Buildings and building improvements (2)		41,961	41,616	[2]
Leasehold improvements (2)		24,441	23,561	[2]
Data processing equipment and software		36,302	35,469
Machinery, equipment, furniture and fixtures		71,465	68,666
Construction in Progress, Gross		6,512	6,940
Property, plant and equipment, gross		182,863	178,434
Accumulated depreciation		(110,493)	(102,367)
Property, plant and equipment, net		72,370	76,067
Accrued expenses and other current liabilities:
Accrued customer obligations (3)	[3]	26,292	34,918
Wages and benefits		18,188	44,505
Commissions and professional fees		2,024	5,549
Dividends Payable, Current		7,582	8,057
Deferred rent		1,721	1,847
Severance		1,500	1,415
Other		7,226	9,687
Accrued expenses and other current liabilities		$ 64,533	$ 105,978

[1] All short-term investments were classified as available-for-sale and were measured at fair value based on level one measurement, or quoted market prices, as defined by ASC 820. The Company did not recognize any realized gains or losses on the sale of investments during the fiscal years ended 2019 and 2018.

[2] Certain balances as at September 29, 2018 relating to property, plant and equipment have been reclassified. These reclassifications have no impact to the Consolidated Balance Sheet as at September 29, 2018.

[3] Represents customer advance payments, customer credit program, accrued warranty expense and accrued retrofit obligations.