Note 5 - Loans (Details Textual)		3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Performing Financial Instruments [Member]
Impaired Financing Receivable, Recorded Investment	$ 7,400,000	$ 7,400,000		$ 7,400,000		$ 6,900,000
Troubled Debt Restructuring [Member]
Financing Receivable, Modifications, Number of Contracts	110
Reserve for Unfunded Commitments Included in Other Liabilities	$ 695,000	695,000		695,000		695,000
Loans and Leases Receivable, Impaired, Commitment to Lend	0	0		0		0
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	2,900,000	$ 2,900,000		$ 2,900,000		2,300,000
Financing Receivable, Modifications, Subsequent Default, Number of Contracts		0	0	0	0
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans		$ 93,000	$ 127,000	$ 249,000	$ 287,000
Impaired Financing Receivable, Recorded Investment	17,933,000	17,933,000		$ 17,933,000		21,390,000
Percentage of Collateral Coverage to Loan Balance to Consider Restructured Loan to Performing and Accrual Status				100.00%
Financing Receivable, Modifications, Recorded Investment	$ 11,200,000	$ 11,200,000		$ 11,200,000		$ 15,900,000
Financing Receivable, Modifications, Number of Contracts	119	2	3	4	10
Troubled Debt Restructurings Percentage of Gross Portfolio Loans	1.43%	1.43%		1.43%		2.22%
Doubtful Grade Remaining Outstanding Period, Minimum				180 days
Loans and Leases Receivable, Allowance	$ 11,849,000	$ 11,849,000		$ 11,849,000		$ 11,180,000
Percentage of Allowance for Loan and Lease Losses out of Net Loans	1.52%	1.52%		1.52%		1.56%
Fair Value Disclosure, Off-balance Sheet Risks, Amount, Asset	$ 222,100,000	$ 222,100,000		$ 222,100,000		$ 230,600,000
Percentage of Loan Portfolio Secured by Real Estate	76.00%	76.00%		76.00%
Percentage of Unallocated Allowance Amount out of Allowance for Loan and Lease Losses				3.00%		5.00%
Maximum Loan to Value, Percentage				80.00%