Share-Based Compensation - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended		90 Months Ended
	Mar. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Oct. 31, 2019
Stock options
Stock Option and Compensation Plans
Unrecognized share-based compensation costs for option awards, net of estimated forfeitures		$ 7,300		$ 7,300		$ 7,300
Expected weighted average period to recognize share-based compensation costs (in years)				2 years 8 months 12 days
Restricted stock units
Stock Option and Compensation Plans
Expected weighted average period to recognize share-based compensation costs (in years)				2 years 7 months 6 days
Unrecognized compensation costs, net of estimated forfeitures		$ 4,400		$ 4,400		$ 4,400
Employee stock purchase plan
Stock Option and Compensation Plans
Common stock issued (in shares)		0	0	43,581	31,522
Proceeds from stock plans				$ 42	$ 41
2013 Plan
Stock Option and Compensation Plans
Increase in number of shares available under the Plan (in shares)				1,985,000		10,539,000
Annual increase in shares reserved for issuance under the Plan (as a percent)				4.00%
Number of shares of common stock available for issuance under the Plan (in shares)		2,774,000		2,774,000		2,774,000
2013 Plan | Employee stock purchase plan
Stock Option and Compensation Plans
Number of shares available for future purchase (in shares)		838,182		838,182		838,182
2019 Inducement Plan | Stock options
Stock Option and Compensation Plans
Increase in number of shares available under the Plan (in shares)	1,000,000
Number of shares of common stock available for issuance under the Plan (in shares)		897,000		897,000		897,000
Number of initial shares reserved for issuance under the Plan (in shares)							1,000,000