Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 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	$ 2,760		$ 1,846		$ 10,650	$ 5,513
Stock Options
Outstanding (in shares)	4,625,768				4,625,768
Outstanding, weighted-average exercise price (in dollars per share)	$ 12.20				$ 12.20
Granted (in shares)					1,701,258
Granted (in dollars per share)					$ 13.64
Stock options | Research and development
Stock option and incentive plans
Total compensation cost	$ 1,060		701		$ 3,333	2,108
Stock options | General and administrative
Stock option and incentive plans
Total compensation cost	1,700		1,145		7,317	3,405
Restricted stock
Stock option and incentive plans
Total compensation cost	$ 81		3		$ 217	$ 8
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		$ 3		$ 217	$ 8
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)	1,017,372				1,017,372
2014 Plan | Stock options
Stock Options
Outstanding (in shares)	3,291,558				3,291,558
Granted (in shares)					1,082,324
Equity Incentive Plan, Employee Inducements | Stock options
Stock Options
Outstanding (in shares)	1,327,645				1,327,645
Granted (in shares)					618,934