CONDENSED CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS EQUITY (DEFICIT) (unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock, beginning balance at Dec. 31, 2018	$ 89,404					$ 89,404
Redeemable convertible preferred stock, beginning balance, shares at Dec. 31, 2018	18,474,742					18,474,742
Beginning balance at Dec. 31, 2018	$ (106,388)	$ 1	$ 9,131	$ (15)	$ (115,505)
Beginning balance, shares at Dec. 31, 2018		3,085,307
Issuance of common stock warrants	572		572
Elimination of fractional shares upon reverse stock split (see Note 8)		$ (1)	1
Redeemable convertible preferred stock, Elimination of fractional shares upon reverse stock split (see Note8)						(39)
Elimination of fractional shares upon reverse stock split (see Note 8), shares		(34)
Exercise of common stock warrants	8		8
Exercise of common stock warrants, shares		207,712
Conversion of Series A, B and C redeemable convertible preferred stock to common stock	89,404	$ 2	89,402
Redeemable convertible preferred stock, Conversion of Series A, B and C redeemable convertible preferred stock to common stock, shares						(18,474,703)
Redeemable convertible preferred stock, Conversion of Series A, B and C redeemable convertible preferred stock to common stock						$ (89,404)
Conversion of Series A, B and C redeemable convertible preferred stock to common stock, shares		18,474,703
Conversion of redeemable convertible preferred stock warrants to common stock warrants	2,086		2,086
Proceeds from initial public offering, net of expenses	140,024	$ 1	140,023
Proceeds from initial public offering, net of expenses, shares		9,109,725
Proceeds from exercise of stock options	611		611
Proceeds from exercise of stock options, shares		244,192
Stock-based compensation	2,255		2,255
Net loss	(11,554)				(11,554)
Ending balance at Jun. 30, 2019	117,018	$ 3	244,089	(15)	(127,059)
Ending balance, shares at Jun. 30, 2019		31,121,605
Redeemable convertible preferred stock, beginning balance at Mar. 31, 2019						$ 89,404
Redeemable convertible preferred stock, beginning balance, shares at Mar. 31, 2019						18,474,742
Beginning balance at Mar. 31, 2019	(110,523)	$ 1	10,666		(121,190)
Beginning balance, shares at Mar. 31, 2019		3,166,316
Elimination of fractional shares upon reverse stock split (see Note 8)		$ (1)	1
Redeemable convertible preferred stock, Elimination of fractional shares upon reverse stock split (see Note8)						(39)
Elimination of fractional shares upon reverse stock split (see Note 8), shares		(34)
Exercise of common stock warrants	8		8
Exercise of common stock warrants, shares		207,712
Conversion of Series A, B and C redeemable convertible preferred stock to common stock	89,404	$ 2	89,402
Redeemable convertible preferred stock, Conversion of Series A, B and C redeemable convertible preferred stock to common stock, shares						(18,474,703)
Redeemable convertible preferred stock, Conversion of Series A, B and C redeemable convertible preferred stock to common stock						$ (89,404)
Conversion of Series A, B and C redeemable convertible preferred stock to common stock, shares		18,474,703
Conversion of redeemable convertible preferred stock warrants to common stock warrants	2,086		2,086
Proceeds from initial public offering, net of expenses	140,024	$ 1	140,023
Proceeds from initial public offering, net of expenses, shares		9,109,725
Proceeds from exercise of stock options	257		257
Proceeds from exercise of stock options, shares		163,183
Stock-based compensation	1,646		1,646
Foreign currency translation adjustment	(15)			(15)
Net loss	(5,869)				(5,869)
Ending balance at Jun. 30, 2019	117,018	$ 3	244,089	(15)	(127,059)
Ending balance, shares at Jun. 30, 2019		31,121,605
Beginning balance at Dec. 31, 2019	106,690	$ 3	247,282	(6)	(140,589)
Beginning balance, shares at Dec. 31, 2019		31,243,029
Proceeds from exercise of stock options	1,013		1,013
Proceeds from exercise of stock options, shares		513,993
Proceeds from Employee Stock Purchase Plan purchases	631		631
Proceeds from Employee Stock Purchase Plan purchases, shares		71,480
Restricted stock units released, shares		43,620
Stock-based compensation	3,071		3,071
Foreign currency translation adjustment	(9)			(9)
Unrealized gain on available-for-sale debt securities	121			121
Net loss	(18,394)				(18,394)
Ending balance at Jun. 30, 2020	93,123	$ 3	251,997	106	(158,983)
Ending balance, shares at Jun. 30, 2020		31,872,122
Beginning balance at Mar. 31, 2020	99,202	$ 3	248,854	73	(149,728)
Beginning balance, shares at Mar. 31, 2020		31,530,443
Proceeds from exercise of stock options	690		690
Proceeds from exercise of stock options, shares		236,578
Proceeds from Employee Stock Purchase Plan purchases	631		631
Proceeds from Employee Stock Purchase Plan purchases, shares		71,480
Restricted stock units released, shares		33,621
Stock-based compensation	1,822		1,822
Foreign currency translation adjustment	(4)			(4)
Unrealized gain on available-for-sale debt securities	37			37
Net loss	(9,255)				(9,255)
Ending balance at Jun. 30, 2020	$ 93,123	$ 3	$ 251,997	$ 106	$ (158,983)
Ending balance, shares at Jun. 30, 2020		31,872,122