Share-Based Compensation - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended		94 Months Ended
	Feb. 28, 2021	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Oct. 31, 2019
Stock options
Stock Option and Compensation Plans
Unrecognized share-based compensation costs for option awards, net of estimated forfeitures			$ 14,500		$ 14,500		$ 14,500
Expected weighted average period to recognize share-based compensation costs (in years)					3 years
Restricted stock units
Stock Option and Compensation Plans
Expected weighted average period to recognize share-based compensation costs (in years)					2 years 9 months 18 days
Unrecognized compensation costs, net of estimated forfeitures			$ 8,000		$ 8,000		$ 8,000
Employee stock purchase plan
Stock Option and Compensation Plans
Common stock issued (in shares)			0	0	24,422	43,581
Proceeds from stock plans					$ 121	$ 42
2013 Plan
Stock Option and Compensation Plans
Increase in number of shares available under the Plan (in shares)					2,542,000		13,081,000
Number of shares of common stock available for issuance under the Plan (in shares)			2,847,000		2,847,000		2,847,000
2013 Plan | Employee stock purchase plan
Stock Option and Compensation Plans
Number of shares available for future purchase (in shares)			780,939		780,939		780,939
2019 Inducement Plan | Stock options
Stock Option and Compensation Plans
Increase in number of shares available under the Plan (in shares)	600,000	1,000,000
Number of shares of common stock available for issuance under the Plan (in shares)			731,000		731,000		731,000
Number of initial shares reserved for issuance under the Plan (in shares)								1,000,000