Fair value of financial instruments - Additional Quantitative Information about Assets Measured at Fair Value on Nonrecurring Basis (Details) - Nonrecurring Basis - Impaired Loans - Level 3 - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value Inputs, Assets, Quantitative Information
Assets measured at fair value	$ 4,740	$ 220
Minimum
Fair Value Inputs, Assets, Quantitative Information
Range and weighted average of appraisal adjustments	22.80%	21.60%
Range and weighted average of liquidation expenses	3.00%	3.00%
Maximum
Fair Value Inputs, Assets, Quantitative Information
Range and weighted average of appraisal adjustments	82.40%	97.00%
Range and weighted average of liquidation expenses	6.00%	6.00%
Weighted Average
Fair Value Inputs, Assets, Quantitative Information
Range and weighted average of appraisal adjustments	63.60%	77.70%
Range and weighted average of liquidation expenses	5.20%	4.90%