Summary of Significant Accounting Policies - Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of diluted net loss per share (in shares)	7,372,631	6,078,234	4,312,445
Common stock warrants
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of diluted net loss per share (in shares)	180,274	242,779	242,779
Restricted Stock Units
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of diluted net loss per share (in shares)		147,554	264,361
Common stock options
Anti-dilutive securities
Anti-dilutive securities excluded from the calculation of diluted net loss per share (in shares)	7,192,357	5,687,901	3,805,305