Stock Options And Employee Stock Purchase Plan (Summary Of Stock Option Activity And Weighted Average Exercise Prices) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Options
Options outstanding, beginning balance	(8,843,413)	8,816,760	8,711,808
Options granted	3,463,500	3,642,600	3,809,380
Options exercised	(1,634,658)	(2,278,451)	(2,843,547)
Options cancelled	(830,776)	(1,337,496)	(860,881)
Options outstanding, ending balance	(9,841,479)	(8,843,413)	8,816,760
Options exercisable	3,220,228	2,805,399	3,097,748
Weighted Average Exercise Price
Options outstanding, beginning balance	$ 7.91	$ 5.04	$ 3.82
Options granted	$ 16.20	$ 12.24	$ 7.13
Options exercised	$ 5.10	$ 4.28	$ 4.10
Options cancelled	$ 10.78	$ 7.03	$ 5.09
Options outstanding, ending balance	$ 11.06	$ 7.91	$ 5.04
Options exercisable	$ 6.61	$ 4.63	$ 3.93