Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders’ Equity (Deficit) - USD ($) $ in Thousands	Series A Redeemable convertible preferred stock Preferred Stock [Member]	Series B Redeemable convertible preferred stock Preferred Stock [Member]	Common stock	Additional paid-in capital	Accumulated other comprehensive loss	Accumulated deficit	Total
Balance at Beginning of period at Dec. 31, 2018	$ 33,112	$ 91,038
Balance at Beginning of period (in shares) at Dec. 31, 2018	22,501,174	63,032,500
Increase (Decrease) in Temporary Equity [Roll Forward]
Sale of Series B redeemable convertible preferred stock, net of stock issue costs of $19		431,034
Sale of Series B redeemable convertible preferred stock, net of stock issue costs of $19		$ 481
Accretion of redeemable convertible preferred stock to redemption value	$ 444	1,581
Balance at Ending period at Mar. 31, 2019	$ 33,556	$ 93,100
Balance at Ending period (in shares) at Mar. 31, 2019	22,501,174	63,463,534
Balance at Beginning of period at Dec. 31, 2018						$ (137,860)	$ (137,860)
Balance at Beginning of period (in shares) at Dec. 31, 2018			295,717
Increase (Decrease) in Temporary Equity [Roll Forward]
Vesting of common stock previously subject to repurchase (in shares)			130
Exercise of stock options (in shares)			398
Exercise of stock options				$ 3			3
Foreign currency translation adjustment					$ (4)		(4)
Stock-based compensation expense				60			60
Accretion of redeemable convertible preferred stock to redemption value				(63)		(1,962)	(2,025)
Net loss						(5,966)	(5,966)
Balance at Ending period at Mar. 31, 2019					(4)	(145,788)	(145,792)
Balance at Ending period (in shares) at Mar. 31, 2019			296,245
Balance at Beginning of period at Dec. 31, 2019			$ 11	198,829	(19)	(167,859)	30,962
Balance at Beginning of period (in shares) at Dec. 31, 2019			11,406,221
Increase (Decrease) in Temporary Equity [Roll Forward]
Vesting of common stock previously subject to repurchase (in shares)			90
Vesting of common stock previously subject to repurchase				1			$ 1
Exercise of stock options (in shares)			1,289				1,289
Exercise of stock options				8			$ 8
Foreign currency translation adjustment					27		27
Stock-based compensation expense				449			449
Net loss						(7,220)	(7,220)
Balance at Ending period at Mar. 31, 2020			$ 11	$ 199,287	$ 8	$ (175,079)	$ 24,227
Balance at Ending period (in shares) at Mar. 31, 2020			11,407,600