Summary of Significant Accounting Policies - Potentially Dilutive Shares (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in the calculation of diluted net loss per share (in shares)	12,634,061	13,413,024	7,573,251
Common stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in the calculation of diluted net loss per share (in shares)	2,403,055	1,781,388	38,675
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in the calculation of diluted net loss per share (in shares)	10,231,006	11,631,636	7,534,576