Common stock (Details) - $ / shares	Dec. 31, 2022	Dec. 31, 2021	Oct. 31, 2015
Class of Stock [Line Items]
Common Stock, Shares Authorized	120,000,000	120,000,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Shares available for future issuance (in shares)	12,778,375	11,990,940
2015 Stock Option Plan
Class of Stock [Line Items]
Shares available for future issuance (in shares)	3,536,932	4,374,539	1,311,812
2015 Employee Stock Purchase Plan.
Class of Stock [Line Items]
Shares available for future issuance (in shares)	1,884,309	1,659,574
Stock options
Class of Stock [Line Items]
Shares available for future issuance (in shares)	6,199,571	5,013,193
Unvested restricted common stock units
Class of Stock [Line Items]
Shares available for future issuance (in shares)	1,112,563	806,379
Founders restricted stock
Class of Stock [Line Items]
Shares available for future issuance (in shares)	45,000	137,255