Retirement plans (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 0.50
Defined Contribution Retirement Plan Employee Contribution	$ 1.00
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	4.00%
Defined Contribution Retirement Plan Vesting Period	3 months
Defined Contribution Plan Contributions Made by Employer and Employee	$ 164,000	$ 159,000	$ 150,000
Bank Owned Life Insurance Income	185,000	183,000	182,000
Proceeds from Life Insurance Policies	448,000	0	0
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Bank Owned Life Insurance Income	$ 183,000	182,000
Defined Contribution Retirement Plan Participant Approval Period	60 days
Deferred Compensation Arrangement with Individual, Requisite Service Period	10 years
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Total	$ 2,064,000	1,972,000
Defined Contribution Plan, Cost Recognized	168,000	201,000	257,000
Life Insurance, Corporate or Bank Owned, Change in Value	37,000
Proceeds from Life Insurance Policies	266,000
Directors Deferral Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Total	166,000	82,000
Defined Contribution Plan, Cost Recognized	89,000	87,000	$ 123,000
Common Stock, Shares Held in Employee Trust	$ 1,034,382	$ 1,034,382
Common Stock, Shares Held in Employee Trust, Shares	48,055	48,055