Short-term borrowings (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets Sold Under Agreements To Repurchase [Line Items]
Total repurchase agreements	$ 5,192	$ 77,050
Repurchase agreement
Assets Sold Under Agreements To Repurchase [Line Items]
Total repurchase agreements	4,842	1,700
Repurchase agreement | U.S. Treasury and U.S. government sponsored entities
Assets Sold Under Agreements To Repurchase [Line Items]
Total repurchase agreements	94	55
Repurchase agreement | State and political subdivisions
Assets Sold Under Agreements To Repurchase [Line Items]
Total repurchase agreements	2,990	627
Repurchase agreement | Mortgage-backed securities - residential
Assets Sold Under Agreements To Repurchase [Line Items]
Total repurchase agreements	1,389	948
Repurchase agreement | Collateralized mortgage obligations
Assets Sold Under Agreements To Repurchase [Line Items]
Total repurchase agreements	$ 369	$ 70