Summary of Significant Accounting Policies - Net Loss Per Share (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Antidilutive common stock equivalents excluded from computation of diluted net loss per share
Anti-dilutive securities excluded from the calculation of diluted net loss per share (in shares)	2,863,973	2,510,975	2,863,973	2,510,975
Stock options
Antidilutive common stock equivalents excluded from computation of diluted net loss per share
Anti-dilutive securities excluded from the calculation of diluted net loss per share (in shares)	2,839,407	2,486,409	2,839,407	2,486,409
Common stock warrants
Antidilutive common stock equivalents excluded from computation of diluted net loss per share
Anti-dilutive securities excluded from the calculation of diluted net loss per share (in shares)	24,566	24,566	24,566	24,566