Segment Information - Information About Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jul. 01, 2012	Jun. 30, 2013	Jul. 01, 2012
Segment Reporting Information [Line Items]
Product revenue	$ 79,698	$ 78,449	$ 154,370	$ 149,856
Service revenue	6,812	5,877	13,032	12,179
Operating income	20,173	23,350	38,154	41,091
MVSD [Member]
Segment Reporting Information [Line Items]
Product revenue	72,012	69,743	140,331	133,964
Service revenue	2,301	1,778	4,393	3,698
Operating income	23,527	25,035	45,603	46,179
SISD [Member]
Segment Reporting Information [Line Items]
Product revenue	7,686	8,706	14,039	15,892
Service revenue	4,511	4,099	8,639	8,481
Operating income	2,227	2,848	3,959	5,240
Reconciling Items [Member]
Segment Reporting Information [Line Items]
Operating income	$ (5,581)	$ (4,533)	$ (11,408)	$ (10,328)