Net Income (Loss) Per Share Attributable to Common Stockholders and Pro Forma Net Loss Per Share (Details 1)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Potentially dilutive securities not included in the calculation of diluted net income (loss) per share
Total potentially dilutive securities	124,044,994	91,396,856	124,044,994	89,399,040
Common stock options [Member]
Potentially dilutive securities not included in the calculation of diluted net income (loss) per share
Total potentially dilutive securities	38,134,900	7,390,998	38,134,900	5,527,537
Convertible preferred stock [Member]
Potentially dilutive securities not included in the calculation of diluted net income (loss) per share
Total potentially dilutive securities	83,703,016	83,703,016	83,703,016	83,703,016
RSUs [Member]
Potentially dilutive securities not included in the calculation of diluted net income (loss) per share
Total potentially dilutive securities	1,032,304		1,032,304
Common stock subject to repurchase [Member]
Potentially dilutive securities not included in the calculation of diluted net income (loss) per share
Total potentially dilutive securities	473,103	302,842	473,103	168,487
ESPP obligations [Member]
Potentially dilutive securities not included in the calculation of diluted net income (loss) per share
Total potentially dilutive securities	701,671		701,671