Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2017	$ (72,328)			$ 948	$ (73,234)	$ (42)
Balance, shares at Dec. 31, 2017		30,459,574
Balance at Dec. 31, 2017		$ 226,196
Balance, shares at Dec. 31, 2017			3,278,129
Conversion of preferred stock to common stock	226,198		$ 3	226,195
Conversion of preferred stock to common stock, shares		(30,459,574)
Conversion of preferred stock to common stock		$ (226,196)
Conversion of preferred stock to common stock, shares			30,459,574
Issuance of common stock upon IPO	124,735		$ 1	124,734
Issuance of common stock upon IPO, shares			9,200,000
Issuance of common stock upon exercise of stock options, net of amounts related to unvested shares	95			95
Issuance of common stock upon exercise of stock options, net of amounts related to unvested shares, shares			67,349
Vesting of early exercised stock options and restricted stock	1,276			1,276
Vesting of early exercised stock options and restricted stock, shares			528,374
Issuance of common stock under Employee Stock Purchase Plan	751			751
Issuance of common stock under Employee Stock Purchase Plan, shares			77,397
Stock-based compensation	3,874			3,874
Other comprehensive income (loss)	(65)					(65)
Net loss	(49,594)				(49,594)
Balance at Dec. 31, 2018	$ 234,942		$ 4	357,873	(122,828)	(107)
Balance, shares at Dec. 31, 2018		0
Balance, shares at Dec. 31, 2018	44,537,946		43,610,823
Cumulative effect adjustment upon adoption of ASC 606 | ASC 606	$ 2,212				2,212
Issuance of common stock upon exercise of stock options, net of amounts related to unvested shares	$ 188			188
Issuance of common stock upon exercise of stock options, net of amounts related to unvested shares, shares	41,762		34,780
Vesting of early exercised stock options and restricted stock	$ 1,029			1,029
Vesting of early exercised stock options and restricted stock, shares			417,883
Issuance of common stock under Employee Stock Purchase Plan	1,029			1,029
Issuance of common stock under Employee Stock Purchase Plan, shares			148,709
Stock-based compensation	8,981			8,981
Other comprehensive income (loss)	171					171
Net loss	(84,710)				(84,710)
Balance at Dec. 31, 2019	$ 163,842		$ 4	$ 369,100	$ (205,326)	$ 64
Balance, shares at Dec. 31, 2019		0
Balance, shares at Dec. 31, 2019	45,925,004		44,212,195