Consolidated Statements of Convertible Preferred Stock, Redeemable Common Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Convertible Preferred Stock	Redeemable Common Stock
Beginning balance, convertible preferred stock (in share) at Dec. 31, 2016						22,061,973	107,371
Beginning balance, convertible preferred stock at Dec. 31, 2016						$ 34,307	$ 734
Increase (Decrease) in Temporary Equity [Roll Forward]
Repurchase of Series Seed convertible preferred stock, net of issuance costs of $11	$ 0
Issuance cost of convertible preferred stock, net of issuance cost (in shares)						15,956,995
Issuance costs of convertible preferred stock, net of issuance costs	0					$ 26,596
Conversion of redeemable common stock into common stock	0
Ending balance, convertible preferred stock (in shares) at Dec. 31, 2017						38,018,968	107,371
Ending balance, convertible preferred stock at Dec. 31, 2017						$ 60,903	$ 734
Beginning balance (in shares) at Dec. 31, 2016		345,856
Beginning balance at Dec. 31, 2016	(23,052)	$ 0	$ 884	$ 0	$ (23,936)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		4,751
Exercise of stock options	9		9
Stock-based compensation expense	492		492
Net loss	(21,994)				(21,994)
Ending balance (in shares) at Dec. 31, 2017		350,607
Ending balance at Dec. 31, 2017	(44,545)	$ 0	1,385	0	(45,930)
Increase (Decrease) in Temporary Equity [Roll Forward]
Repurchase of Series Seed convertible preferred stock, net of issuance cost of $11,000 (in shares)						(598,975)
Repurchase of Series Seed convertible preferred stock, net of issuance costs of $11	(22)				(22)	$ (517)
Issuance cost of convertible preferred stock, net of issuance cost (in shares)						2,659,574
Issuance costs of convertible preferred stock, net of issuance costs	0					$ 4,289
Conversion of redeemable common stock into common stock	$ 0
Ending balance, convertible preferred stock (in shares) at Dec. 31, 2018	40,079,567					40,079,567	107,371
Ending balance, convertible preferred stock at Dec. 31, 2018	$ 64,675					$ 64,675	$ 734
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		1,045
Exercise of stock options	7		7
Stock-based compensation expense	759		759
Net loss	(33,285)				(33,285)
Ending balance (in shares) at Dec. 31, 2018		351,652
Ending balance at Dec. 31, 2018	(77,086)	$ 0	2,151	0	(79,237)
Increase (Decrease) in Temporary Equity [Roll Forward]
Repurchase of Series Seed convertible preferred stock, net of issuance costs of $11	0
Conversion of redeemable common stock into common stock (in shares)		107,364					(107,371)
Conversion of redeemable common stock into common stock	734		734				$ (734)
Conversion of convertible preferred shares into common stock (in shares)		3,808,430				(40,079,567)
Conversion of convertible preferred shares into common stock	64,675	$ 4	64,671			$ (64,675)
Ending balance, convertible preferred stock (in shares) at Dec. 31, 2019						0	0
Ending balance, convertible preferred stock at Dec. 31, 2019						$ 0	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exchange of common stock in connection with Merger (in shares)		2,440,582
Exchange of common stock in connection with Merger	45,541	$ 2	45,539
Fair value of replacement equity awards	817		817
Reclassification of warrant liability to permanent equity	5,235		5,235
Issuance of common stock and prefunded warrants for the purchase of common stock, net of issuance costs of $11.5 million (in shares)		9,336,667
Issuance of common stock and prefunded warrants for the purchase of common stock, net of issuance costs of $11.4 million	$ 139,388	$ 9	139,379
Exercise of stock options (in shares)	51,617	50,321
Exercise of stock options	$ 345	$ 1	344
Exercise of warrants (in shares)		33,846
Exercise of warrants	447		447
Stock-based compensation expense	2,050		2,050
Foreign currency translation adjustment	(119)			(119)
Net loss	(52,807)				(52,807)
Ending balance (in shares) at Dec. 31, 2019		16,128,862
Ending balance at Dec. 31, 2019	$ 129,220	$ 16	$ 261,367	$ (119)	$ (132,044)