Consolidated Statements Of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Consolidated Statements Of Income [Abstract]
Revenue	$ 106,394	$ 100,869
Costs and expenses
Cost of revenue	47,448	45,679
Selling, general and administrative	18,003	17,109
Research and development	9,718	8,995
Total costs and expenses	75,169	71,783
Operating income	31,225	29,086
Equity in net loss of affiliate	(2,356)	(2,532)
Income before interest and income tax expense	28,869	26,554
Interest income	20	6
Interest expense	129	164
Income before income tax expense	28,760	26,396
Income tax expense	10,953	10,149
Net income	$ 17,807	$ 16,247
Income per weighted-average common share
Basic	$ 0.65	$ 0.60
Diluted	$ 0.64	$ 0.59
Weighted-average common shares used in calculations
Basic	27,246	27,079
Potentially dilutive securities	496	516
Diluted	27,742	27,595
Dividends declared per common share outstanding	$ 0.10	$ 0.10