CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenue
Product	$ 295,588	$ 297,310	$ 263,463
Service	28,691	24,604	27,228
Total revenue	324,279	321,914	290,691
Cost of revenue
Product	65,432	64,732	61,497
Service	14,063	13,187	16,091
Total cost of revenue	79,495	77,919	77,588
Gross margin
Product	230,156	232,578	201,966
Service	14,628	11,417	11,137
Total gross margin	244,784	243,995	213,103
Research, development, and engineering expenses	41,549	40,946	33,080
Selling, general, and administrative expenses	119,828	117,694	104,235
Restructuring charges (Note 16)			75
Operating Income	83,407	85,355	75,713
Foreign currency loss	(880)	(504)	(328)
Investment income	4,470	2,902	1,421
Other expense	(367)	(636)	(703)
Income before income tax expense	86,630	87,117	76,103
Income tax expense	18,532	17,248	14,722
Net income	$ 68,098	$ 69,869	$ 61,381
Net income per common and common-equivalent share:
Basic	$ 1.59	$ 1.67	$ 1.54
Diluted	$ 1.56	$ 1.63	$ 1.52
Weighted-average common and common-equivalent shares outstanding:
Basic	42,833	41,859	39,924
Diluted	43,640	42,762	40,297
Cash dividends per common share	$ 1.54	$ 0.36	$ 0.25