Summary of significant accounting policies - Narrative (Details)	6 Months Ended
	Jun. 30, 2022 USD ($) segment	Jan. 01, 2022 USD ($)	Dec. 31, 2021 USD ($)	Jun. 30, 2021 USD ($)
Summary of significant accounting policies
Number of operating segments | segment	1
Restricted cash	$ 100,000		$ 100,000	$ 100,000
Deferred offering costs	300,000		$ 300,000
Operating lease liability		$ 200,000
Operating right-of-use asset, net	$ 182,000	$ 200,000