CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Stockholders' equity, beginning of period (in shares) at Dec. 31, 2019		25,163,803
Stockholders' equity, beginning of period at Dec. 31, 2019	$ 63,008	$ 3	$ 258,121	$ 464	$ (195,580)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from public offering, net of underwriting discounts, commissions and offering costs (in shares)		3,135,053
Issuance of common stock from public offering, net of underwriting discounts, commissions and offering costs	62,978		62,978
Issuance of common stock upon exercise of stock options, net of shares withheld (in shares)		43,334
Issuance of common stock upon exercise of stock options, net of shares withheld	174		174
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
Net unrealized gain (loss) on marketable securities	221			221
Net loss	(12,772)				(12,772)
Stockholders' equity, end of period (in shares) at Mar. 31, 2020		28,406,128
Stockholders' equity, end of period at Mar. 31, 2020	116,270	$ 3	323,922	697	(208,352)
Stockholders' equity, beginning of period (in shares) at Dec. 31, 2019		25,163,803
Stockholders' equity, beginning of period at Dec. 31, 2019	63,008	$ 3	258,121	464	(195,580)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Foreign currency translation	(23)
Net unrealized gain (loss) on marketable securities	(11)
Net loss	(34,718)
Stockholders' equity, end of period (in shares) at Sep. 30, 2020		28,838,577
Stockholders' equity, end of period at Sep. 30, 2020	102,031	$ 3	331,896	430	(230,298)
Stockholders' equity, beginning of period (in shares) at Mar. 31, 2020		28,406,128
Stockholders' equity, beginning of period at Mar. 31, 2020	116,270	$ 3	323,922	697	(208,352)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options, net of shares withheld (in shares)		46,608
Issuance of common stock upon exercise of stock options, net of shares withheld	185		185
Issuance of common stock related to employee stock purchase plan (in shares)		74,685
Issuance of common stock related to employee stock purchase plan	991		991
Issuance of common stock upon vesting of restricted stock units (in shares)		85,030
Stock-based compensation	2,955		2,955
Vesting of early exercised stock options	26		26
Foreign currency translation	(2)			(2)
Net unrealized gain (loss) on marketable securities	(85)			(85)
Net loss	(12,472)				(12,472)
Stockholders' equity, end of period (in shares) at Jun. 30, 2020		28,612,451
Stockholders' equity, end of period at Jun. 30, 2020	107,868	$ 3	328,079	610	(220,824)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options, net of shares withheld (in shares)		137,392
Issuance of common stock upon exercise of stock options, net of shares withheld	628		628
Issuance of common stock upon vesting of restricted stock units (in shares)		88,734
Stock-based compensation	3,180		3,180
Vesting of early exercised stock options	9		9
Foreign currency translation	(33)			(33)
Net unrealized gain (loss) on marketable securities	(147)			(147)
Net loss	(9,474)				(9,474)
Stockholders' equity, end of period (in shares) at Sep. 30, 2020		28,838,577
Stockholders' equity, end of period at Sep. 30, 2020	102,031	$ 3	331,896	430	(230,298)
Stockholders' equity, beginning of period (in shares) at Dec. 31, 2020		32,583,220
Stockholders' equity, beginning of period at Dec. 31, 2020	169,363	$ 3	408,113	524	(239,277)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options, net of shares withheld (in shares)		93,975
Issuance of common stock upon exercise of stock options, net of shares withheld	601		601
Issuance of common stock upon vesting of restricted stock units (in shares)		131,339
Stock-based compensation	4,030		4,030
Vesting of early exercised stock options	9		9
Foreign currency translation	(115)			(115)
Net unrealized gain (loss) on marketable securities	21			21
Net loss	(12,242)				(12,242)
Stockholders' equity, end of period (in shares) at Mar. 31, 2021		32,808,534
Stockholders' equity, end of period at Mar. 31, 2021	161,667	$ 3	412,753	430	(251,519)
Stockholders' equity, beginning of period (in shares) at Dec. 31, 2020		32,583,220
Stockholders' equity, beginning of period at Dec. 31, 2020	$ 169,363	$ 3	408,113	524	(239,277)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options, net of shares withheld (in shares)	317,001
Foreign currency translation	$ (103)
Net unrealized gain (loss) on marketable securities	5
Net loss	(42,095)
Stockholders' equity, end of period (in shares) at Sep. 30, 2021		33,450,995
Stockholders' equity, end of period at Sep. 30, 2021	143,618	$ 3	424,561	426	(281,372)
Stockholders' equity, beginning of period (in shares) at Mar. 31, 2021		32,808,534
Stockholders' equity, beginning of period at Mar. 31, 2021	161,667	$ 3	412,753	430	(251,519)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options, net of shares withheld (in shares)		140,917
Issuance of common stock upon exercise of stock options, net of shares withheld	650		650
Issuance of common stock related to employee stock purchase plan (in shares)		104,861
Issuance of common stock related to employee stock purchase plan	1,566		1,566
Issuance of common stock upon vesting of restricted stock units (in shares)		181,958
Stock-based compensation	4,257		4,257
Vesting of early exercised stock options	9		9
Foreign currency translation	35			35
Net unrealized gain (loss) on marketable securities	(5)			(5)
Net loss	(13,981)				(13,981)
Stockholders' equity, end of period (in shares) at Jun. 30, 2021		33,236,270
Stockholders' equity, end of period at Jun. 30, 2021	154,198	$ 3	419,235	460	(265,500)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options, net of shares withheld (in shares)		82,109
Issuance of common stock upon exercise of stock options, net of shares withheld	1,076		1,076
Issuance of common stock upon vesting of restricted stock units (in shares)		132,616
Stock-based compensation	4,241		4,241
Vesting of early exercised stock options	9		9
Foreign currency translation	(23)			(23)
Net unrealized gain (loss) on marketable securities	(11)			(11)
Net loss	(15,872)				(15,872)
Stockholders' equity, end of period (in shares) at Sep. 30, 2021		33,450,995
Stockholders' equity, end of period at Sep. 30, 2021	$ 143,618	$ 3	$ 424,561	$ 426	$ (281,372)