Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended				6 Months Ended		15 Months Ended
	Apr. 05, 2019	May 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020
Common Stock
Net proceeds from issuance of common stock		$ 48,327					$ 63,025	$ 10,068
Common Stock
Common Stock
Number of shares issued			9,735,649	2,657,823	1,180,367	1,318,481
Common Stock | Follow-on Offering
Common Stock
Common stock, price per share		$ 5.50
Number of shares issued		8,181,819
Common Stock | Over-allotment Option
Common Stock
Common stock, price per share		$ 5.17
Number of shares issued		1,227,272
Common Stock | 2019 Sales Agreement
Common Stock
Maximum aggregate proceeds from offering	$ 50,000
Number of shares issued			326,558				2,984,381		10,321,840
Net proceeds from issuance of common stock			$ 1,667				$ 14,357		$ 46,983