Common Stock (Details)	Sep. 30, 2012	Dec. 31, 2011
Common stock outstanding and reserved shares of common stock for future issuance
Options outstanding	37,279,442	39,601,640
RSUs	1,134,851
Stock awards available for future grants:
Total reserved shares of common stock for future issuance	55,049,594
2005 Stock Option Plan [Member]
Stock awards available for future grants:
Total reserved shares of common stock for future issuance	56,231,262
2012 Equity Incentive Plan [Member]
Stock awards available for future grants:
Total reserved shares of common stock for future issuance	11,635,301
2012 Employee Stock Purchase Plan [Member]
Stock awards available for future grants:
Total reserved shares of common stock for future issuance	5,000,000