Condensed Consolidated Statements of Earnings (Loss) - (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 28, 2014	Sep. 29, 2013	Sep. 28, 2014	Sep. 29, 2013
Income Statement [Abstract]
Net sales	$ 99,957	$ 103,632	$ 303,643	$ 307,075
Costs and expenses:
Cost of goods sold	67,458	71,631	206,706	215,888
Selling, general and administrative expenses	13,899	17,829	43,353	52,662
Research and development expenses	5,807	5,718	16,765	17,741
Restructuring and impairment charges	1,570	901	4,806	8,107
Operating earnings	11,223	7,553	32,013	12,677
Other (expense)/income:
Interest expense	(568)	(818)	(1,763)	(2,782)
Interest income	707	441	1,959	1,300
Other	562	490	(1,618)	381
Total other income (expense)	701	113	(1,422)	(1,101)
Earnings from continuing operations before taxes	11,924	7,666	30,591	11,576
Income tax expense	3,807	2,551	11,033	13,727
Earnings (loss) from continuing operations	8,117	5,115	19,558	(2,151)
Discontinued operations
Earnings from discontinued operations, net of tax		1,704		1,203
Net earnings (loss)	$ 8,117	$ 6,819	$ 19,558	$ (948)
Basic:
Continuing operations	$ 0.24	$ 0.16	$ 0.58	$ (0.06)
Discontinued operations		$ 0.04		$ 0.03
Basic net earnings (loss) per share	$ 0.24	$ 0.20	$ 0.58	$ (0.03)
Diluted:
Continuing operations	$ 0.24	$ 0.16	$ 0.57	$ (0.06)
Discontinued operations		$ 0.05		$ 0.03
Diluted net earnings (loss) per share	$ 0.24	$ 0.21	$ 0.57	$ (0.03)
Basic weighted-average common shares outstanding	33,599	33,696	33,683	33,603
Effect of dilutive securities	508	635	515
Diluted weighted-average common shares outstanding	34,107	34,331	34,198	33,603
Cash dividends declared per share	$ 0.040	$ 0.035	$ 0.120	$ 0.105