Income taxes - Textual (Details) - USD ($)		3 Months Ended		6 Months Ended
	Jun. 29, 2020	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Income Tax Disclosure [Abstract]
Income tax benefit related to operating losses and research and development tax credits		$ 0	$ 0	$ 0	$ 0
Income tax benefits		$ 0		$ 0
Amount of state tax that can be offset by NOLs and credits for a three year period	$ 5,000,000
State taxable income amount that can be reduced by NOLs for a three year period	$ 1,000,000