CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013		Dec. 31, 2012
Revenue
Product	$ 451,066	$ 326,786		$ 295,588
Service	35,204	27,100		28,691
Total revenue	486,270	353,886		324,279
Cost of revenue
Product	101,448	71,893		65,432
Service	19,572	12,187		14,063
Total cost of revenue	121,020	84,080		79,495
Gross margin
Product	349,618	254,893		230,156
Service	15,632	14,913		14,628
Total gross margin	365,250	269,806		244,784
Research, development, and engineering expenses	59,920	48,087		41,549
Selling, general, and administrative expenses	161,667	135,351		119,828
Operating income	143,663	86,368		83,407
Foreign currency gain (loss)	861	(646)		(880)
Investment income	3,156	2,604		4,470
Other expense	(283)	(440)		(367)
Income before income tax expense	147,397	87,886		86,630
Income tax expense	25,912	14,313		18,532
Net income	$ 121,485	$ 73,573		$ 68,098
Net income per common and common-equivalent share:
Basic (in dollars per share)	$ 1.40	$ 0.85	[1]	$ 0.79	[1]
Diluted (in dollars per share)	$ 1.36	$ 0.83	[1]	$ 0.78	[1]
Weighted-average common and common-equivalent shares outstanding:
Basic (in dollars per share)	86,858	86,946	[1]	85,666	[1]
Diluted (in dollars per share)	89,071	88,901	[1]	87,280	[1]
Cash dividends per common share (in dollars per share)				$ 0.77	[1]

[1] Prior period results have been adjusted to reflect the two-for-one stock split effected in the form of a stock dividend which occurred in the third quarter of 2013.