Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Follow-on Public Offering	July 13, 2020	August 10, 2020	Common Stock	Common Stock Follow-on Public Offering	Common Stock August 2019	Common Stock July 13, 2020	Common Stock July 20, 2020	Common Stock September 30, 2020	Common Stock August 10, 2020	Common Stock March 20, 2019	Common Stock May 17, 2019	Common Stock June 12, 2019	Common Stock March 12, 2020	Common Stock June 30, 2020	Additional Paid-in Capital	Additional Paid-in Capital Follow-on Public Offering	Additional Paid-in Capital July 13, 2020	Additional Paid-in Capital August 10, 2020	Accumulated Deficit	Accumulated Other Comprehensive Income/(Loss)
Beginning balance at Dec. 31, 2018	$ 5,369				$ 1												$ 76,348				$ (71,020)	$ 40
Beginning balance, shares at Dec. 31, 2018					11,534,190
Net loss	(40,243)																				(40,243)
Issuance of restricted common stock, shares							84,975					2,406,618	19,407	64,982
Issuance of common stock, including underwriter's over-allotment, net of offering costs and underwriter's discount	29,607				$ 1												29,606
Issuance of common stock, including underwriter's over-allotment, net of offering costs and underwriter's discount, shares					3,600,000
Stock-based compensation	24,747																24,747
Exercise of stock options	$ 2																2
Exercise of stock options, shares	487				487
Other comprehensive income (loss)	$ 26																					26
Ending balance at Sep. 30, 2019	19,508				$ 2												130,703				(111,263)	66
Ending balance, shares at Sep. 30, 2019					17,710,659
Beginning balance at Jun. 30, 2019	23,115				$ 2												119,348				(96,288)	53
Beginning balance, shares at Jun. 30, 2019					17,625,241
Net loss	(14,975)																				(14,975)
Issuance costs from Initial Public Offering	(21)																(21)
Issuance of restricted common stock, shares							84,975
Stock-based compensation	11,374																11,374
Exercise of stock options	2																2
Exercise of stock options, shares					443
Other comprehensive income (loss)	13																					13
Ending balance at Sep. 30, 2019	19,508				$ 2												130,703				(111,263)	66
Ending balance, shares at Sep. 30, 2019					17,710,659
Beginning balance at Dec. 31, 2019	10,727				$ 2												140,477				(129,809)	57
Beginning balance, shares at Dec. 31, 2019					17,736,649
Net loss	(18,772)																				(18,772)
Issuance of restricted common stock			$ 49	$ 760															$ 49	$ 760
Issuance of restricted common stock, shares					22,700			10,000	95,500	22,700	90,000				439,145	134,364
Forfeiture of restricted common stock, shares															(371,329)	(134,366)
Issuance of common stock, including underwriter's over-allotment, net of offering costs and underwriter's discount		$ 23,416																$ 23,416
Issuance of common stock, including underwriter's over-allotment, net of offering costs and underwriter's discount, shares						3,860,710
Shares of restricted common stock retired in connection with vesting	(139)																(139)
Shares of restricted common stock retired in connection with vesting, shares					(41,299)
Issuance of 25,000 warrants on August 18, 2020	204																204
Stock-based compensation	17,192																17,192
Exercise of stock options	$ 12																12
Exercise of stock options, shares	2,870				2,870
Other comprehensive income (loss)	$ (28)																					(28)
Ending balance at Sep. 30, 2020	33,421				$ 2												181,971				(148,581)	29
Ending balance, shares at Sep. 30, 2020					21,844,944
Beginning balance at Jun. 30, 2020	5,222				$ 2												152,948				(147,776)	48
Beginning balance, shares at Jun. 30, 2020					17,763,164
Net loss	(805)																				(805)
Issuance of restricted common stock			$ 49	$ 760															$ 49	$ 760
Issuance of restricted common stock, shares					22,700			10,000	95,500	22,700	90,000
Issuance of common stock, including underwriter's over-allotment, net of offering costs and underwriter's discount		$ 23,416																$ 23,416
Issuance of common stock, including underwriter's over-allotment, net of offering costs and underwriter's discount, shares						3,860,710
Issuance of 25,000 warrants on August 18, 2020	204																204
Stock-based compensation	4,582																4,582
Exercise of stock options	12																12
Exercise of stock options, shares					2,870
Other comprehensive income (loss)	(19)																					(19)
Ending balance at Sep. 30, 2020	$ 33,421				$ 2												$ 181,971				$ (148,581)	$ 29
Ending balance, shares at Sep. 30, 2020					21,844,944