Consolidated Statements of Income (Unaudited) (USD $) In Thousands, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Consolidated Statements of Income [Abstract]
Revenue	$ 105,563	$ 99,470	$ 302,169	$ 283,705
Costs and expenses
Cost of revenue	49,388	50,384	156,092	153,041
Selling, general and administrative	18,401	18,137	54,166	54,927
Research and development	9,444	10,088	27,456	29,069
Total costs and expenses	77,233	78,609	237,714	237,037
Operating income	28,330	20,861	64,455	46,668
Equity in net income (loss) of affiliate	(2,290)	(2,639)	631	472
Income before interest and income tax expense	26,040	18,222	65,086	47,140
Interest income	6	4	20	10
Interest expense	109	226	377	745
Income before income tax expense	25,937	18,000	64,729	46,405
Income tax expense	10,586	6,672	25,547	17,530
Net income	$ 15,351	$ 11,328	$ 39,182	$ 28,875
Income per weighted-average common share
Basic	$ 0.56	$ 0.42	$ 1.44	$ 1.08
Diluted	$ 0.55	$ 0.42	$ 1.42	$ 1.07
Weighted-average common shares used in calculations
Basic	27,222	26,834	27,154	26,693
Potentially dilutive securities	461	263	475	339
Diluted	27,683	27,097	27,629	27,032
Dividends declared per common share outstanding	$ 0.10	$ 0.10	$ 0.30	$ 0.30