Allowance for loan losses (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Loans and Leases Receivable, Allowance	$ 3,373,000	$ 3,562,000	$ 5,729,000	$ 7,239,000
Allowance for Loan and Lease Loss, Recovery of Bad Debts	355,000	649,000	771,000
Allowance for Loan and Lease Losses, Write-offs	544,000	816,000	2,381,000
Provision for Loan and Lease Losses	0	(2,000,000)	100,000
Unallocated Financing Receivable [Member]
Loans and Leases Receivable, Allowance	713,000	59,000
Commercial Real Estate Portfoliio [Member]
Allowance for Loan and Lease Loss, Recovery of Bad Debts	730,000	866,000
Allowance for Loan and Lease Losses, Write-offs	$ 111,000	$ 90,000	$ 1,220,000
Percentage Of Recovery Loss On Portfolio From Historical Experience	0.20%	0.57%	0.96%
Consumer Real Estate Portfoliio [Member]
Allowance for Loan and Lease Loss, Recovery of Bad Debts		$ 1,143,000
Allowance for Loan and Lease Losses, Write-offs		$ 215,000	$ 562,000
Percentage Of Recovery Loss On Portfolio From Historical Experience	22.00%	0.24%	1.36%
Construction and Land Development [Member]
Loans and Leases Receivable, Allowance	$ 341,000	$ 321,000	$ 236,000	1,409,000
Allowance for Loan and Lease Loss, Recovery of Bad Debts	11,000	51,000	46,000
Allowance for Loan and Lease Losses, Write-offs	10,000	252,000	100,000
Increase (Decrease) in Finance Receivables			$ 1,643,000	$ 12,945,000
Percentage Of Recovery Loss On Portfolio From Historical Experience			0.27%
Provision for Loan and Lease Losses	$ 19,000	$ 286,000	$ (1,119,000)