Derivatives and hedging activities - Effect of Fair Value and Cash Flow Hedge Accounting on the Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative Instruments, Gain (Loss)
Total amounts of income and expense line items presented in the statements of income and comprehensive income in which the effects of fair value or cash flow hedges are recorded	$ (128)	$ (137)	$ (22)	$ 356
Interest income
Derivative Instruments, Gain (Loss)
Total amounts of income and expense line items presented in the statements of income and comprehensive income in which the effects of fair value or cash flow hedges are recorded	137	133	405	279
Amount of gain or (loss) reclassified from accumulated other comprehensive income into income	137	133	405	279
Amount of gain or (loss) reclassified from accumulated other comprehensive income into income - included component	153	149	453	327
Amount of gain or (loss) reclassified from accumulated other comprehensive income into income - excluded component	$ (16)	(16)	(48)	(48)
Interest expense
Derivative Instruments, Gain (Loss)
Total amounts of income and expense line items presented in the statements of income and comprehensive income in which the effects of fair value or cash flow hedges are recorded		(20)	(48)	53
Amount of gain or (loss) reclassified from accumulated other comprehensive income into income		(20)	(23)	53
Amount of gain or (loss) reclassified from accumulated other comprehensive income into income as a result that a forecasted transaction is no longer probable of occurring			(25)
Amount of gain or (loss) reclassified from accumulated other comprehensive income into income - included component		$ (20)	$ (48)	$ 53