Consolidated Statements of Income (Unaudited) (USD $) In Thousands, except Per Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Consolidated Statements of Income [Abstract]
Revenue	$ 95,737	$ 88,339	$ 196,606	$ 184,235
Costs and expenses
Cost of revenue	61,025	59,504	106,704	102,657
Selling, general and administrative	18,656	19,149	35,765	36,790
Research and development	9,017	9,072	18,012	18,981
Total costs and expenses	88,698	87,725	160,481	158,428
Operating income	7,039	614	36,125	25,807
Equity in net income of affiliate	5,453	5,642	2,921	3,111
Income before interest and income tax expense	12,492	6,256	39,046	28,918
Interest income	8	4	14	6
Interest expense	104	254	268	519
Income before income tax expense	12,396	6,006	38,792	28,405
Income tax expense	4,812	2,207	14,961	10,858
Net income	$ 7,584	$ 3,799	$ 23,831	$ 17,547
Income per weighted-average common share
Basic	$ 0.28	$ 0.14	$ 0.88	$ 0.66
Diluted	$ 0.27	$ 0.14	$ 0.86	$ 0.65
Weighted-average common shares used in calculations
Basic	27,159	26,650	27,119	26,622
Potentially dilutive securities	449	424	483	377
Diluted	27,608	27,074	27,602	26,999
Dividends declared per common share outstanding	$ 0.10	$ 0.10	$ 0.20	$ 0.20