Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jul. 01, 2012	Jun. 30, 2013	Jul. 01, 2012
Revenue
Product	$ 79,698	$ 78,449	$ 154,370	$ 149,856
Service	6,812	5,877	13,032	12,179
Total revenue	86,510	84,326	167,402	162,035
Cost of revenue
Product	17,910	17,635	34,374	33,191
Service	3,240	2,914	6,199	6,416
Total cost of revenue	21,150	20,549	40,573	39,607
Gross margin
Product	61,788	60,814	119,996	116,665
Service	3,572	2,963	6,833	5,763
Total gross margin	65,360	63,777	126,829	122,428
Research, development, and engineering expenses	11,887	10,300	23,208	20,661
Selling, general, and administrative expenses	33,300	30,127	65,467	60,676
Operating income	20,173	23,350	38,154	41,091
Foreign currency gain (loss)	76	(30)	139	(668)
Investment income	774	1,801	1,166	2,773
Other expense	(257)	(99)	(140)	(96)
Income before income tax expense	20,766	25,022	39,319	43,100
Income tax expense	3,946	5,255	6,916	9,051
Net income	$ 16,820	$ 19,767	$ 32,403	$ 34,049
Earnings per weighted-average common and common-equivalent share:
Basic	$ 0.39	$ 0.46	$ 0.75	$ 0.80
Diluted	$ 0.38	$ 0.45	$ 0.73	$ 0.78
Weighted-average common and common-equivalent shares outstanding:
Basic	43,522	42,851	43,392	42,710
Diluted	44,357	43,601	44,251	43,599
Cash dividends per common share	$ 0.00	$ 0.11	$ 0.00	$ 0.21