Stockholders' equity - Additional Information (Details) $ / shares in Units, $ in Thousands		12 Months Ended
	Jan. 01, 2022 shares	Dec. 31, 2022 USD ($) d offering $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Nov. 04, 2021 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized (in shares)		100,000,000	100,000,000
Common stock, par value (in dollars per share) | $ / shares		$ 0.000001	$ 0.000001
Common stock, shares issued (in shares)		42,648,346	42,457,471
Common stock, shares outstanding (in shares)		42,648,346	42,457,471
Outstanding pre-funded warrants (in shares)		12,663,010	12,663,010
Exercise price (in dollars per share) | $ / shares		$ 0.000001
Percentage of outstanding stock per stockholder, upon notice, maximum		19.99%
Notice period | d		61
Preferred stock, shares authorized (in shares)		5,000,000	5,000,000
Preferred stock, par value (in dollars per share) | $ / shares		$ 0.000001	$ 0.000001
Preferred stock, shares issued (in shares)		0	0
Preferred stock, shares outstanding (in shares)		0	0
Options outstanding (in shares)		8,514,381	8,963,945
Options exercised (in shares)		36,500
Common stock issued upon exercise of options aggregate intrinsic value | $		$ 100	$ 1,300
Weighted-average grant date fair value of options granted (in dollars per share) | $ / shares		$ 0.95	$ 6.37
Stock-based compensation expense | $		$ 8,829	$ 11,557
Unrecognized stock-based compensation cost (in dollars per share) | $		$ 13,400
Unrecognized stock-based compensation cost, weighted-average period recognized (in years)		2 years 1 month 24 days
Proceeds from ESPP | $		$ 82	$ 372
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		1 year
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		4 years
2014 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares of common stock that may be issued (in shares)		13,408,356
Shares of common stock reserved for issuance percentage		4.00%
Number of additional shares authorized (in shares)	2,212,454
Award expiration period (in years)		10 years
Shares available to be granted (in shares)		6,705,058	5,040,300
Equity Incentive Plan 2006
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding (in shares)		0
Common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercised (in shares)		36,500	124,928
Issuance of shares under Employee Stock Purchase Plan (in shares)		129,625	51,747
Pre-funded warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding pre-funded warrants (in shares)		12,663,010
Percentage of outstanding stock per stockholder, maximum		9.99%
Shares issuable under 2020 ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Sale of shares under public offering (in dollars per share) | $ / shares		$ 0.83	$ 9.53
Issuance of shares under Employee Stock Purchase Plan (in shares)		75,881	22,972
Shares issuable under 2020 ESPP | 2020 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Sale of shares under public offering (in dollars per share) | $ / shares		$ 0.36	$ 5.33
ESPP common stock reserved for issuance (in shares)		759,936
ESPP max contribution rate		15.00%
ESPP purchase price of common stock, percent of market price		85.00%
ESPP number of offerings per year | offering		2
ESPP offering period		6 months
Issuance of shares under Employee Stock Purchase Plan (in shares)		53,744	28,775
Proceeds from ESPP | $		$ 100	$ 400
Equity Offering Sales Agreement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum value | $				$ 40,000