CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK, REDEEMABLE COMMON STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Series Seed, A and B Convertible Preferred	Redeemable Common Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Convertible preferred shares, beginning balance, shares at Dec. 31, 2018		40,079,567
Convertible preferred shares, beginning balance at Dec. 31, 2018		$ 64,675
Increase (Decrease) in Temporary Equity [Roll Forward]
Conversion of convertible preferred shares into common stock, shares		(40,079,567)		3,808,430
Conversion of convertible preferred shares into common stock	$ 64,675	$ (64,675)		$ 4	$ 64,671
Convertible preferred shares, ending balance, shares at Mar. 31, 2019		0
Convertible preferred shares, ending balance at Mar. 31, 2019		$ 0
Beginning balance, shares at Dec. 31, 2018			107,364	351,652
Beginning balance at Dec. 31, 2018	(77,086)		$ 734	$ 0	2,151	$ 0	$ (79,237)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of redeemable common stock into common stock, shares			107,364	107,364
Conversion of redeemable common stock into common stock	733		$ (734)	$ 0	733
Exchange of common stock in connection with Merger, 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
Exercise of stock options, shares				16,483
Exercise of stock options	113				113
Stock-based compensation expense	262				262
Currency translation adjustment	23					23
Net loss	(10,873)						(10,873)
Ending balance, shares at Mar. 31, 2019			0	6,724,511
Ending balance at Mar. 31, 2019	29,440		$ 0	$ 6	119,521	23	(90,110)
Convertible preferred shares, beginning balance, shares at Dec. 31, 2018		40,079,567
Convertible preferred shares, beginning balance at Dec. 31, 2018		$ 64,675
Beginning balance, shares at Dec. 31, 2018			107,364	351,652
Beginning balance at Dec. 31, 2018	(77,086)		$ 734	$ 0	2,151	0	(79,237)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of redeemable common stock into common stock	734
Net loss	(41,970)
Ending balance, shares at Sep. 30, 2019				12,436,205
Ending balance at Sep. 30, 2019	79,107			$ 12	200,421	(119)	(121,207)
Convertible preferred shares, beginning balance, shares at Mar. 31, 2019		0
Convertible preferred shares, beginning balance at Mar. 31, 2019		$ 0
Convertible preferred shares, ending balance, shares at Jun. 30, 2019		0
Convertible preferred shares, ending balance at Jun. 30, 2019		$ 0
Beginning balance, shares at Mar. 31, 2019			0	6,724,511
Beginning balance at Mar. 31, 2019	29,440		$ 0	$ 6	119,521	23	(90,110)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Shares, New Issues				5,670,000
Stock Issued During Period, Value, New Issues	79,297			$ 6	79,291
Exercise of stock options, shares				700
Exercise of stock options	5				5
Exercise of warrants	440				440
Stock Issued During Period Shares Warrants Exercised				33,846
Stock-based compensation expense	433				433
Currency translation adjustment	(65)					(65)
Net loss	(13,383)						(13,383)
Ending balance, shares at Jun. 30, 2019			0	12,429,057
Ending balance at Jun. 30, 2019	96,167		$ 0	$ 12	199,690	(42)	(103,493)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options, shares				7,148
Exercise of stock options	40				40
Stock-based compensation expense	691				691
Currency translation adjustment	(77)					(77)
Net loss	(17,714)						(17,714)
Ending balance, shares at Sep. 30, 2019				12,436,205
Ending balance at Sep. 30, 2019	79,107			$ 12	200,421	(119)	(121,207)
Beginning balance, shares at Dec. 31, 2019				16,128,862
Beginning balance at Dec. 31, 2019	129,220			$ 16	261,367	(119)	(132,044)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options, shares				13,006
Exercise of stock options	96				96
Stock-based compensation expense	613				613
Net loss	(11,138)						(11,138)
Ending balance, shares at Mar. 31, 2020				16,141,868
Ending balance at Mar. 31, 2020	118,791			$ 16	262,076	(119)	(143,182)
Beginning balance, shares at Dec. 31, 2019				16,128,862
Beginning balance at Dec. 31, 2019	129,220			$ 16	261,367	(119)	(132,044)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of redeemable common stock into common stock	$ 0
Exercise of stock options, shares	17,689
Net loss	$ (43,731)
Ending balance, shares at Sep. 30, 2020	16,286,645
Ending balance at Sep. 30, 2020	$ 89,708			$ 16	265,586	(119)	(175,775)
Beginning balance, shares at Mar. 31, 2020				16,141,868
Beginning balance at Mar. 31, 2020	118,791			$ 16	262,076	(119)	(143,182)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options, shares				407
Exercise of stock options	2				2
Issuance of shares under employee stock purchase plan, shares				10,057
Issuance of shares under employee stock purchase plan	76				76
Vesting of restricted stock units, less shares withheld and retired to satisfy tax obligations, shares				23,822
Vesting of restricted stock units, less shares withheld and retired to satisfy tax obligations	(14)			$ (14)
Stock-based compensation expense	1,173				1,173
Net loss	$ (15,144)						(15,144)
Ending balance, shares at Jun. 30, 2020	16,176,154
Ending balance at Jun. 30, 2020	$ 104,884			$ 16	263,313	(119)	(158,326)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options, shares				4,276
Exercise of stock options	29				29
Vesting of restricted stock units, less shares withheld and retired to satisfy tax obligations	2,244			$ 2,244
Stock-based compensation expense	(17,449)
Net loss	$ (17,449)
Ending balance, shares at Sep. 30, 2020	16,286,645
Ending balance at Sep. 30, 2020	$ 89,708			$ 16	$ 265,586	$ (119)	$ (175,775)