Note 8 - Fair Value Measurements (Details Textual) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Financial and Nonfinancial Liabilities, Fair Value Disclosure	$ 0		$ 0		$ 0
Provision for Loan and Lease Losses, Total	316,000	$ 256,000	513,000	$ 467,000
Impaired Loan [Member]
Provision for Loan and Lease Losses, Total	72,000	3,000	137,000	5,000
Foreclosed Real Estate [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Write-down or Reserve, Amount	$ 419,000	$ 0	$ 419,000	$ 228,000
Fair Value, Inputs, Level 3 [Member] | Impaired Loan [Member] | Minimum [Member]
Fair Value Inputs, Estimated Selling Costs			14.00%		14.00%
Fair Value, Inputs, Level 3 [Member] | Impaired Loan [Member] | Maximum [Member]
Fair Value Inputs, Estimated Selling Costs			100.00%		62.00%
Fair Value, Inputs, Level 3 [Member] | Impaired Loan [Member] | Weighted Average [Member]
Fair Value Inputs, Estimated Selling Costs			70.00%		39.00%
Fair Value, Inputs, Level 3 [Member] | Foreclosed Real Estate [Member] | Minimum [Member]
Fair Value Inputs, Estimated Selling Costs			10.00%		17.00%
Fair Value, Inputs, Level 3 [Member] | Foreclosed Real Estate [Member] | Maximum [Member]
Fair Value Inputs, Estimated Selling Costs			79.00%		75.00%
Fair Value, Inputs, Level 3 [Member] | Foreclosed Real Estate [Member] | Weighted Average [Member]
Fair Value Inputs, Estimated Selling Costs			51.00%		45.00%