Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Shares
Conversion of Series A convertible preferred stock (in shares)	178
Number of common shares issued for each convertible Series A preferred stock	915,000			915,000
Deemed Dividends
Deemed dividends on Series A convertible preferred stock			$ 8,900
Series A Convertible Preferred Stock
Shares
Preferred stock, shares outstanding	4,575			4,575		4,753
Common Stock
Shares
Conversion of Series A convertible preferred stock (in shares)	35,600
Stock options
Stock option and incentive plans
Total compensation cost	$ 2,910	$ 1,792		$ 7,890	$ 3,667
Stock Options
Outstanding (in shares)	4,622,470			4,622,470
Outstanding, weighted-average exercise price (in dollars per share)	$ 12.25			$ 12.25
Granted (in shares)				1,585,662
Granted (in dollars per share)				$ 13.57
Stock options | Research and development
Stock option and incentive plans
Total compensation cost	$ 1,083	678		$ 2,273	1,407
Stock options | General and administrative
Stock option and incentive plans
Total compensation cost	1,827	1,114		5,617	2,260
Restricted stock
Stock option and incentive plans
Total compensation cost	$ 81	4		$ 136	$ 5
Shares
Issued (in shares)				15,000	5,250
Outstanding (in shares)	37,000			37,000
Restricted stock | Minimum
Stock option and incentive plans
Vesting period				1 year
Restricted stock | Maximum
Stock option and incentive plans
Vesting period				3 years
Restricted stock | General and administrative
Stock option and incentive plans
Total compensation cost	$ 81	$ 4		$ 136	$ 5
2005 Plan
Stock option and incentive plans
Common stock reserved for issuance (in shares)	0			0
2005 Plan | Stock options
Stock Options
Outstanding (in shares)	6,565			6,565
2014 Plan
Stock option and incentive plans
Common stock reserved for issuance (in shares)	941,507			941,507
2014 Plan | Stock options
Stock Options
Outstanding (in shares)	3,292,114			3,292,114
Granted (in shares)				1,026,666
Equity Incentive Plan, Employee Inducments | Stock options
Stock Options
Outstanding (in shares)	1,323,791			1,323,791
Granted (in shares)				558,996