SUPPLEMENTAL BALANCE SHEET INFORMATION (Details 3) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 27, 2014	Sep. 28, 2013	Dec. 28, 2013
Accrued Warranty Obligations
Balance at beginning of year	$ 3,285	$ 3,528
Additions charged to cost of sales	2,134	1,817
Warranty claims	(2,487)	(2,112)
Balance at end of period	2,932	3,233
Accrued Expenses and Other Current Liabilities
Deferred revenue	13,059		13,609
Deferred lease liability	5,165		5,448
Accrued and deferred taxes	4,144		3,130
Short-term accrued warranty obligations	2,760		3,093
Other	8,910		10,061
Accrued expenses and other current liabilities, total	34,038		35,341
Accumulated Other Comprehensive Loss
Cumulative foreign currency translation losses	(9,870)		(2,296)
Unrecognized net pension losses, net of tax	(2,093)		(2,399)
Unrealized gains on marketable securities, net of tax	899		1,076
Accumulated other comprehensive loss	$ (11,064)		$ (3,619)