Net income (loss) per share (Details 2) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share	1,282	4,665	1,696	4,665
Employee Stock Options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share	1,256	3,735	1,670	3,735
Restricted stock units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share	26	668	26	668
Employee Stock Purchase Plan [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share		258		258
Common Stock Warrants [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share		4		4