Commitments and contingencies (Details) - USD ($)
$ in Thousands |
Sep. 30, 2017 |
Dec. 31, 2016 |
| Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |
|
|
| Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability |
$ 77,693
|
$ 76,179
|
| Standby Letters of Credit [Member] |
|
|
| Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |
|
|
| Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability |
4,213
|
4,397
|
| Undisbursed credit lines [Member] |
|
|
| Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |
|
|
| Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability |
55,999
|
55,315
|
| Commitments to extend or originate credit [Member] |
|
|
| Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |
|
|
| Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability |
$ 17,481
|
$ 16,467
|