CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Stockholders' equity (deficit), beginning of period at Dec. 31, 2018	$ 90,192	$ 3	$ 246,927	$ 439	$ (157,177)
Stockholders' equity (deficit), beginning of period (in shares) at Dec. 31, 2018		24,450,757
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options, net of shares withheld	125		125
Issuance of common stock upon exercise of stock options, net of shares withheld (in shares)		46,809
Stock-based compensation	1,871		1,871
Vesting of early exercised stock options	66		66
Additional accrual of IPO related costs	(160)		(160)
Foreign currency translation	(19)			(19)
Unrealized gain on marketable securities	25			25
Net loss	(9,345)				(9,345)
Stockholders' equity (deficit), ending of period (in shares) at Mar. 31, 2019		24,497,566
Stockholders' equity (deficit), ending of period at Mar. 31, 2019	82,755	$ 3	248,829	445	(166,522)
Stockholders' equity (deficit), beginning of period at Dec. 31, 2019	$ 63,008	$ 3	258,121	464	(195,580)
Stockholders' equity (deficit), beginning of period (in shares) at Dec. 31, 2019	25,163,803
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from public offering, net of underwriting discounts, commissions and offering costs	$ 62,978		62,978
Issuance of common stock from public offering, net of underwriting discounts, commissions and offering costs (in shares)		3,135,053
Issuance of common stock upon exercise of stock options, net of shares withheld	$ 174		174
Issuance of common stock upon exercise of stock options, net of shares withheld (in shares)	43,334	43,334
Issuance of common stock upon vesting of restricted stock units	$ 0
Issuance of common stock upon vesting of restricted stock units (in shares)		63,938
Stock-based compensation	2,622		2,622
Vesting of early exercised stock options	27		27
Foreign currency translation	12			12
Unrealized gain on marketable securities	221			221
Net loss	(12,772)				(12,772)
Stockholders' equity (deficit), ending of period (in shares) at Mar. 31, 2020		28,406,128
Stockholders' equity (deficit), ending of period at Mar. 31, 2020	$ 116,270	$ 3	$ 323,922	$ 697	$ (208,352)