Stockholders' Equity (Summary Of Stock Option Activity And Weighted Average Exercise Prices) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Options
Options outstanding, beginning balance	9,841,479	8,843,413	8,816,760
Options granted	2,573,700	3,463,500	3,642,600
Options exercised	(771,810)	(1,634,658)	(2,278,451)
Options cancelled	(1,919,176)	(830,776)	(1,337,496)
Options outstanding, ending balance	9,724,193	9,841,479	8,843,413
Options exercisable	4,090,492	3,220,228	2,805,399
Weighted Average Exercise Price
Options outstanding, beginning balance	$ 11.06	$ 7.91	$ 5.04
Options granted	$ 10.20	$ 16.20	$ 12.24
Options exercised	$ 6.48	$ 5.10	$ 4.28
Options cancelled	$ 13.11	$ 10.78	$ 7.03
Options outstanding, ending balance	$ 10.86	$ 11.06	$ 7.91
Options exercisable	$ 8.71	$ 6.61	$ 4.63