Summary of Significant Accounting Policies - Net Loss Per Share (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 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)	2,826,416	2,112,008	2,826,416	2,112,008
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)	2,801,850	2,087,442	2,801,850	2,087,442
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