Condensed Statement of Stockholders' (Deficit) Equity - USD ($) $ in Thousands	Common Stock Series A Convertible Preferred Stock	Common Stock Series B Convertible Preferred Stock	Common Stock IPO	Common Stock Private Placement	Common Stock Secondary Public Offering	Common Stock	Additional Paid-in Capital Series A Convertible Preferred Stock	Additional Paid-in Capital Series B Convertible Preferred Stock	Additional Paid-in Capital IPO	Additional Paid-in Capital Private Placement	Additional Paid-in Capital Secondary Public Offering	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Series A Convertible Preferred Stock	Series B Convertible Preferred Stock	IPO	Private Placement	Secondary Public Offering	Total
Balance at Dec. 31, 2018												$ 1,665	$ (21,257)							$ (19,592)
Balance (in shares) at Dec. 31, 2018						5,513,531
Increase (Decrease) in Stockholders' Equity
Issuance of common stock warrants in connection with the issuance of convertible preferred stock												80								80
Conversion of convertible preferred stock into common stock upon closing of the IPO		$ 1					$ 6,254	$ 32,052							$ 6,254	$ 32,053
Conversion of convertible preferred stock into common stock upon closing of the IPO (in shares)	3,093,898	4,444,773
Issuance of common stock									$ 34,582	$ 18,348							$ 34,582	$ 18,348
Issuance of common stock (in shares)			4,000,000	1,380,344
Exercise of options for common stock issued under Equity Incentive Plan												226								226
Exercise of options for common stock issued under Equity Incentive Plan (in shares)						81,988
Issuance costs																	$ (5,417)	(1,667)
Exercise of warrants of common stock (in shares)						17,026
Stock-based compensation expense												6,171								6,171
Net loss													(45,513)							(45,513)
Other comprehensive income (loss)														$ (2)						(2)
Balance at Dec. 31, 2019						$ 1						99,378	(66,770)	(2)						32,607
Balance (in shares) at Dec. 31, 2019						18,531,560
Increase (Decrease) in Stockholders' Equity
Issuance of common stock					$ 1						$ 134,127								$ 134,128
Issuance of common stock (in shares)					3,152,712
Exercise of options for common stock issued under Equity Incentive Plan						$ 0						81								$ 81
Exercise of options for common stock issued under Equity Incentive Plan (in shares)						35,027														35,027
Issuance costs										$ (41)								$ (41)	$ (714)
Exercise of warrants of common stock (in shares)						249,978
Stock-based compensation expense												1,331								$ 1,331
Net loss													(12,369)							(12,369)
Other comprehensive income (loss)														91						91
Balance at Mar. 31, 2020						$ 2						$ 234,876	$ (79,139)	$ 89						$ 155,828
Balance (in shares) at Mar. 31, 2020						21,969,277