Consolidated Statements Of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Consolidated Statements Of Income [Abstract]
Revenue	$ 422,310	$ 395,379	$ 384,952
Costs and expenses
Cost of revenue	220,381	215,329	196,269
Selling, general and administrative	78,407	75,255	81,866
Research and development	38,416	39,145	42,008
Restructuring and reorganization			9,968
Total costs and expenses	337,204	329,729	330,111
Operating income	85,106	65,650	54,841
Equity in net income of affiliate	7,255	7,092	7,637
Impairment of investment	(3,477)
Income before interest and income tax expense	88,884	72,742	62,478
Interest income	27	14	49
Interest expense	564	984	1,395
Income before income tax expense	88,347	71,772	61,132
Income tax expense	35,056	27,294	18,972
Net income	$ 53,291	$ 44,478	$ 42,160
Income per weighted-average common share
Basic	$ 1.96	$ 1.66	$ 1.59
Diluted	$ 1.93	$ 1.64	$ 1.58
Weighted-average common shares used in calculations
Basic	27,181	26,759	26,493
Potentially dilutive securities	478	346	183
Diluted	27,659	27,105	26,676
Dividends declared per common share outstanding	$ 0.40	$ 0.40	$ 0.40