Common Stock Warrants and Warrant Liability (Details) - USD ($) $ / shares in Units, $ in Thousands					6 Months Ended	9 Months Ended
	Jun. 28, 2019	Sep. 29, 2017	May 15, 2017	Nov. 29, 2016	Jun. 30, 2019	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	May 22, 2020	Apr. 01, 2020	Dec. 31, 2019
Class of Warrant or Right
Stock purchase price (in dollars per share)									$ 13.00	$ 12.00
Proceeds received from exercise of warrants						$ 0	$ 3,057
2016 Warrants
Class of Warrant or Right
Warrants issued	839,899			1,142,838
Period of time before warrants expire from exercisable date (in years)				5 years
Exercise price per full share of stock (in dollars per share)				$ 12.00
Additional period of time warrants could be exercised as the result of an amendment (in years)	2 years
Warrant amendment charge					$ 700
Warrants, outstanding (in shares)						661,310
Warrants exercises (in shares)						0	254,760
Proceeds received from exercise of warrants							$ 3,100
2016 Warrants | Equity Classified
Class of Warrant or Right
Warrants, outstanding (in shares)						1,881,789	1,881,789	1,881,789			2,136,549
Warrants exercises (in shares)							254,760
2016 Warrants | Liability Classified
Class of Warrant or Right
Warrants, outstanding (in shares)						146,837	146,837	146,837			146,837
Equity, 2016 Warrant
Class of Warrant or Right
Warrants, outstanding (in shares)						585,139
Liability, 2016
Class of Warrant or Right
Warrants, outstanding (in shares)						76,171
Investor warrants
Class of Warrant or Right
Warrants issued			66,666
Stock purchase price (in dollars per share)			$ 22.50
Period of time before warrants expire from exercisable date (in years)			5 years
Period of time after issuance date before warrants will be exercisable (in months)			6 months
Placement agent warrants
Class of Warrant or Right
Warrants issued			4,000
Period of time before warrants expire from exercisable date (in years)			5 years
Exercise price per full share of stock (in dollars per share)			$ 28.125
2017 Warrants
Class of Warrant or Right
Warrants issued		1,296,650
Stock purchase price (in dollars per share)		$ 18.63
Period of time before warrants expire from exercisable date (in years)		5 years
Period of time after issuance date before warrants will be exercisable (in months)		6 months