Condensed Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income	Total
Beginning balance (in shares) at Dec. 31, 2019	31,255,267
Beginning balance at Dec. 31, 2019	$ 31	$ 263,384	$ (191,526)	$ 2	$ 71,891
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	140,370
Exercise of stock options		274			274
Stock-based compensation		1,293			1,293
Net loss			(9,941)		(9,941)
Unrealized gain (loss) on investments, net				440	440
Ending balance (in shares) at Mar. 31, 2020	31,395,637
Ending balance at Mar. 31, 2020	$ 31	264,951	(201,467)	442	63,957
Beginning balance (in shares) at Dec. 31, 2019	31,255,267
Beginning balance at Dec. 31, 2019	$ 31	263,384	(191,526)	2	71,891
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss					(30,608)
Ending balance (in shares) at Sep. 30, 2020	33,889,077
Ending balance at Sep. 30, 2020	$ 34	341,687	(222,135)	152	119,738
Beginning balance (in shares) at Mar. 31, 2020	31,395,637
Beginning balance at Mar. 31, 2020	$ 31	264,951	(201,467)	442	63,957
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise/issuance of common stock (in shares)	1,923,076
Exercise/issuance of common stock	$ 2	70,541			70,543
Exercise of stock options (in shares)	265,467
Exercise of stock options	$ 1	603			604
Issuance of common stock under employee stock purchase plan (in shares)	25,919
Issuance of common stock under employee stock purchase plan		801			801
Stock-based compensation		1,654			1,654
Net loss			(10,353)		(10,353)
Unrealized gain (loss) on investments, net				(126)	(126)
Ending balance (in shares) at Jun. 30, 2020	33,610,099
Ending balance at Jun. 30, 2020	$ 34	338,550	(211,820)	316	127,080
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	278,978
Exercise of stock options		1,131			1,131
Stock-based compensation		2,006			2,006
Net loss			(10,315)		(10,315)
Unrealized gain (loss) on investments, net				(164)	(164)
Ending balance (in shares) at Sep. 30, 2020	33,889,077
Ending balance at Sep. 30, 2020	$ 34	341,687	(222,135)	152	119,738
Beginning balance (in shares) at Dec. 31, 2020	34,249,649
Beginning balance at Dec. 31, 2020	$ 34	346,318	(238,891)	39	107,500
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	163,151
Exercise of stock options		848			848
Issuance of common stock upon release of restricted stock units (in shares)	25,490
Stock-based compensation		3,533			3,533
Net loss			(10,694)		(10,694)
Unrealized gain (loss) on investments, net				(33)	(33)
Ending balance (in shares) at Mar. 31, 2021	34,438,290
Ending balance at Mar. 31, 2021	$ 34	350,699	(249,585)	6	101,154
Beginning balance (in shares) at Dec. 31, 2020	34,249,649
Beginning balance at Dec. 31, 2020	$ 34	346,318	(238,891)	39	$ 107,500
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)					548,699
Net loss					$ (35,118)
Ending balance (in shares) at Sep. 30, 2021	34,854,822
Ending balance at Sep. 30, 2021	$ 35	362,152	(274,009)	1	88,179
Beginning balance (in shares) at Mar. 31, 2021	34,438,290
Beginning balance at Mar. 31, 2021	$ 34	350,699	(249,585)	6	101,154
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	155,443
Exercise of stock options	$ 1	1,030			1,031
Issuance of common stock upon release of restricted stock units (in shares)	2,792
Issuance of common stock under employee stock purchase plan (in shares)	26,884
Issuance of common stock under employee stock purchase plan		1,086			1,086
Stock-based compensation		3,409			3,409
Net loss			(10,539)		(10,539)
Unrealized gain (loss) on investments, net				(3)	(3)
Ending balance (in shares) at Jun. 30, 2021	34,623,409
Ending balance at Jun. 30, 2021	$ 35	356,224	(260,124)	3	96,138
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	230,105
Exercise of stock options		2,242			2,242
Issuance of common stock upon release of restricted stock units (in shares)	1,308
Stock-based compensation		3,686			3,686
Net loss			(13,885)		(13,885)
Unrealized gain (loss) on investments, net				(2)	(2)
Ending balance (in shares) at Sep. 30, 2021	34,854,822
Ending balance at Sep. 30, 2021	$ 35	$ 362,152	$ (274,009)	$ 1	$ 88,179