Condensed Consolidated Statements Of Operations (USD $) In Thousands, except Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Revenues:
Subscriber	$ 85,622	$ 62,066	$ 243,788	$ 182,173
Other	405	712	1,299	2,196
Total revenues	86,027	62,778	245,087	184,369
Cost of revenues (including share-based compensation of $246 and $736 for the three and nine months of 2011, respectively, and $304 and $963 for the three and nine months of 2010, respectively)	15,002	10,732	45,952	31,378
Gross profit	71,025	52,046	199,135	152,991
Operating expenses:
Sales and marketing (including share-based compensation of $350 and $1,049 for the three and nine months of 2011, respectively, and $464 and $1,460 for the three and nine months of 2010, respectively)	15,073	10,878	44,929	32,327
Research, development and engineering (including share-based compensation of $110 and $367 for the three and nine months of 2011, respectively, and $204 and $645 for the three and nine months of 2010, respectively)	4,105	3,008	12,714	8,810
General and administrative (including share-based compensation of $1,542 and $4,532 for the three and nine months of 2011, respectively, and $1,805 and $5,699 for the three and nine months of 2010, respectively)	15,403	10,921	44,037	34,263
Total operating expenses	34,581	24,807	101,680	75,400
Operating earnings	36,444	27,239	97,455	77,591
Interest and other income (expense), net	290	491	262	1,750
Earnings before income taxes	36,734	27,730	97,717	79,341
Income tax expense	11,236	7,896	12,770	23,161
Net earnings	$ 25,498	$ 19,834	$ 84,947	$ 56,180
Net earnings per common share:
Basic	$ 0.55	$ 0.44	$ 1.84	$ 1.26
Diluted	$ 0.54	$ 0.43	$ 1.81	$ 1.23
Weighted average shares outstanding:
Basic	45,993,328	44,716,366	45,498,763	44,488,561
Diluted	46,455,584	45,939,172	46,108,890	45,738,389
Cash dividends paid per common share	$ 0.20		$ 0.20