Fair value of financial instruments - Information about Significant Unobservable Inputs (Level 3) Used in Valuation of Assets Measured at Fair Value on Nonrecurring Basis (Details) - Non-recurring Basis $ in Thousands	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Collateral dependent loans	$ 5,477	$ 6,153
Other real estate owned	6,308	6,662
Significant unobservable inputs (level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Collateral dependent loans	5,477	6,153
Other real estate owned	$ 6,308	$ 6,662
Significant unobservable inputs (level 3) | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Collateral dependent loans, measurement input	0.10	0
Other real estate owned, measurement input	0	0
Significant unobservable inputs (level 3) | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Collateral dependent loans, measurement input	0.35	0.30
Other real estate owned, measurement input	0.15	0.15