Unaudited Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Temporary equity, Balance at Dec. 31, 2019		$ 122,465
Temporary equity, Balance, shares at Dec. 31, 2019		85,093,688
Balance at Dec. 31, 2019	$ (78,237)			$ 5,164	$ 41	$ (83,442)
Balance, shares at Dec. 31, 2019			2,484,848
Stock-based compensation	1,360			1,360
Exercise of stock options	11			11
Exercise of stock options, shares			18,384
Vesting of early exercised stock options	49			49
Vesting of early exercised stock options, shares			97,141
Unrealized gain on investment securities	38				38
Net loss	(17,434)					(17,434)
Temporary equity, Balance at Jun. 30, 2020		$ 122,465
Temporary equity, Balance, shares at Jun. 30, 2020		85,093,688
Balance at Jun. 30, 2020	(94,213)			6,584	79	(100,876)
Balance, shares at Jun. 30, 2020			2,600,373
Temporary equity, Balance at Mar. 31, 2020		$ 122,465
Temporary equity, Balance, shares at Mar. 31, 2020		85,093,688
Balance at Mar. 31, 2020	(85,887)			5,694	(27)	(91,554)
Balance, shares at Mar. 31, 2020			2,534,569
Stock-based compensation	857			857
Exercise of stock options	8			8
Exercise of stock options, shares			17,429
Vesting of early exercised stock options	25			25
Vesting of early exercised stock options, shares			48,375
Unrealized gain on investment securities	106				106
Net loss	(9,322)					(9,322)
Temporary equity, Balance at Jun. 30, 2020		$ 122,465
Temporary equity, Balance, shares at Jun. 30, 2020		85,093,688
Balance at Jun. 30, 2020	(94,213)			6,584	79	(100,876)
Balance, shares at Jun. 30, 2020			2,600,373
Balance at Dec. 31, 2020	$ 89,279		$ 3	210,021	1	(120,746)
Balance, shares at Dec. 31, 2020	25,969,442		25,969,442
Stock-based compensation	$ 3,106			3,106
Exercise of stock options	$ 1,059			1,059
Exercise of stock options, shares	466,811		466,811
Vesting of early exercised stock options	$ 15			15
Vesting of early exercised stock options, shares			21,336
Issuance of common stock from employee stock purchase plan	147			147
Issuance of common stock from employee stock purchase plan, shares			48,335
Unrealized gain on investment securities	6				6
Net loss	(30,353)					(30,353)
Balance at Jun. 30, 2021	$ 63,259		$ 3	214,348	7	(151,099)
Balance, shares at Jun. 30, 2021	26,505,924		26,505,924
Balance at Mar. 31, 2021	$ 76,660		$ 3	212,172	(1)	(135,514)
Balance, shares at Mar. 31, 2021			26,209,327
Stock-based compensation	1,586			1,586
Exercise of stock options	436			436
Exercise of stock options, shares			238,133
Vesting of early exercised stock options	7			7
Vesting of early exercised stock options, shares			10,129
Issuance of common stock from employee stock purchase plan	147			147
Issuance of common stock from employee stock purchase plan, shares			48,335
Unrealized gain on investment securities	8				8
Net loss	(15,585)					(15,585)
Balance at Jun. 30, 2021	$ 63,259		$ 3	$ 214,348	$ 7	$ (151,099)
Balance, shares at Jun. 30, 2021	26,505,924		26,505,924