Stockholders' equity - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Mar. 31, 2021
Class of Stock [Line Items]
Accumulated deficit subject to restriction	$ 10.0
Minimum
Class of Stock [Line Items]
Accumulated profits	10.00%
Stock options
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)		7,504,431
ESPP
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)		1,391,002