CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 28, 2014	Jun. 29, 2013	Jun. 28, 2014	Jun. 29, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 4,163	$ (4,045)	$ 815	$ (16,148)
Other comprehensive income (loss), net of tax
Foreign currency translation adjustments	(380)	1,130	(95)	(2,872)
Adjustments related to postretirement benefits	(124)	31	(80)	90
Change in unrealized gain/loss on investments		(4)		(7)
Other comprehensive income (loss), net of tax	(504)	1,157	(175)	(2,789)
Comprehensive Income (loss)	$ 3,659	$ (2,888)	$ 640	$ (18,937)