Segment Information - Information About Company's Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Oct. 02, 2011	Sep. 30, 2012	Oct. 02, 2011
Segment Reporting Information [Line Items]
Product revenue	$ 72,437	$ 74,165	$ 222,293	$ 220,608
Service revenue	7,639	5,920	19,818	17,264
Operating income	21,803	22,389	62,894	63,799
MVSD [Member]
Segment Reporting Information [Line Items]
Product revenue	64,971	66,404	198,935	200,163
Service revenue	3,291	1,771	6,989	5,574
Operating income	22,664	23,422	68,843	72,036
SISD [Member]
Segment Reporting Information [Line Items]
Product revenue	7,466	7,761	23,358	20,445
Service revenue	4,348	4,149	12,829	11,690
Operating income	2,724	2,891	7,964	5,910
Reconciling Items [Member]
Segment Reporting Information [Line Items]
Operating income	$ (3,585)	$ (3,924)	$ (13,913)	$ (14,147)