Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Apr. 01, 2012 BusinessSegment	Apr. 03, 2011
Information about the Company's segments
Product revenue	$ 71,407	$ 68,877
Service revenue	6,302	5,517
Operating income	17,741	17,368
Segment Information (Textual) [Abstract]
Number of reportable segments	2
MVSD [Member]
Information about the Company's segments
Product revenue	64,221	62,817
Service revenue	1,920	1,969
Operating income	21,144	22,027
SISD [Member]
Information about the Company's segments
Product revenue	7,186	6,060
Service revenue	4,382	3,548
Operating income	2,392	997
Reconciling Items [Member]
Information about the Company's segments
Operating income	$ (5,795)	$ (5,656)