Net Loss per Share - Anti-dilution (Details) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from the calculation of diluted net loss per share attributable to common stockholders	1,792,324	9,184,719	7,294,307
Employee, director and consultant stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from the calculation of diluted net loss per share attributable to common stockholders	1,738,524	500,262
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from the calculation of diluted net loss per share attributable to common stockholders	53,800
Restricted common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from the calculation of diluted net loss per share attributable to common stockholders		759,538	1,239,247
Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from the calculation of diluted net loss per share attributable to common stockholders		7,924,919	6,055,060