Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders’ Equity (Deficit) - USD ($) $ in Thousands	Series A Redeemable convertible preferred stock	Series B Redeemable convertible preferred stock	Common stock	Additional paid-in capital	Accumulated other comprehensive loss	Accumulated deficit	Total
Balance at Beginning of period at Dec. 31, 2016	$ 28,811	$ 52,452
Balance at Beginning of period (in shares) at Dec. 31, 2016	22,501,174	39,543,222
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of Series B redeemable convertible preferred stock upon conversion of promissory notes (in shares)		6,951,175
Issuance of Series B redeemable convertible preferred stock upon conversion of promissory notes		$ 9,462
Sale of Series B redeemable convertible preferred stock, net of stock issue costs of $269, $206, $165 (in shares)		12,931,034
Sale of Series B redeemable convertible preferred stock, net of stock issue costs of $269, $206, $165		$ 14,731
Accretion of redeemable convertible preferred stock to redemption value	$ 2,129	3,764
Balance at Ending period at Dec. 31, 2017	$ 30,940	$ 80,409
Balance at Ending period (in shares) at Dec. 31, 2017	22,501,174	59,425,431
Balance at Beginning of period at Dec. 31, 2016						$ (81,174)	$ (81,174)
Balance at Beginning of period (in shares) at Dec. 31, 2016			286,432
Increase (Decrease) in Temporary Equity [Roll Forward]
Vesting of common stock previously subject to repurchase (in shares)			6,955
Vesting of common stock previously subject to repurchase				$ 31			$ 31
Exercise of stock options (in shares)			404				404
Exercise of stock options				2			$ 2
Stock-based compensation expense				197			197
Accretion of redeemable convertible preferred stock to redemption value				(230)		(5,663)	(5,893)
Net loss						(21,334)	(21,334)
Balance at Ending period at Dec. 31, 2017						(108,171)	(108,171)
Balance at Ending period (in shares) at Dec. 31, 2017			293,791
Increase (Decrease) in Temporary Equity [Roll Forward]
Sale of Series B redeemable convertible preferred stock, net of stock issue costs of $269, $206, $165 (in shares)		3,607,069
Sale of Series B redeemable convertible preferred stock, net of stock issue costs of $269, $206, $165		$ 3,978
Accretion of redeemable convertible preferred stock to redemption value	$ 2,172	6,651
Balance at Ending period at Dec. 31, 2018	$ 33,112	$ 91,038					$ 124,150
Balance at Ending period (in shares) at Dec. 31, 2018	22,501,174	63,032,500					0
Increase (Decrease) in Temporary Equity [Roll Forward]
Vesting of common stock previously subject to repurchase (in shares)			549
Vesting of common stock previously subject to repurchase				5			$ 5
Exercise of stock options (in shares)			1,377				1,377
Exercise of stock options				5			$ 5
Stock-based compensation expense				216			216
Accretion of redeemable convertible preferred stock to redemption value				(226)		(8,597)	(8,823)
Net loss						(21,092)	(21,092)
Balance at Ending period at Dec. 31, 2018						(137,860)	$ (137,860)
Balance at Ending period (in shares) at Dec. 31, 2018			295,717
Increase (Decrease) in Temporary Equity [Roll Forward]
Sale of Series B redeemable convertible preferred stock, net of stock issue costs of $269, $206, $165 (in shares)		12,527,956
Sale of Series B redeemable convertible preferred stock, net of stock issue costs of $269, $206, $165		$ 14,367
Accretion of redeemable convertible preferred stock to redemption value	$ 1,563	$ 6,220
Balance at Ending period (in shares) at Dec. 31, 2019	0	0					0
Increase (Decrease) in Temporary Equity [Roll Forward]
Vesting of common stock previously subject to repurchase (in shares)			628
Vesting of common stock previously subject to repurchase				4			$ 4
Exercise of stock options (in shares)			2,527				2,527
Exercise of stock options				14			$ 14
Issuance/Conversion of convertible preferred stock (in shares)	(22,501,174)	(75,560,456)	6,708,649
Issuance/Conversion of convertible preferred stock	$ (34,675)	$ (111,625)	$ 7	146,293			146,300
Issuance of stock			$ 4	50,625			50,629
Issuance of stock (in shares)			4,398,700
Unrealized loss on available for sales securities					$ (4)		(4)
Foreign currency translation adjustment					(15)		(15)
Stock-based compensation expense				457			457
Accretion of redeemable convertible preferred stock to redemption value				(209)		(7,574)	(7,783)
Conversion of outstanding preferred stock warrants				1,645			1,645
Net loss						(22,425)	(22,425)
Balance at Ending period at Dec. 31, 2019			$ 11	$ 198,829	$ (19)	$ (167,859)	$ 30,962
Balance at Ending period (in shares) at Dec. 31, 2019			11,406,221