Employee retirement plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Retirement Benefits [Abstract]
Employer matching contribution, percent of match	25.00%
Employer matching contribution, percent of employees' gross pay	6.00%
Maximum annual contributions per employee	$ 500
Vesting period (in years)	2 years
Annual vesting percentage	50.00%
Vesting percentage after two years of employment	1
Contributions made	$ 400,000	$ 200,000	$ 200,000