Note 13 - Employee Retirement Benefit Plans (Details Textual) - USD ($)		1 Months Ended		12 Months Ended
	Oct. 11, 2016	Oct. 31, 2016	Jun. 30, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2014	Jul. 01, 2017
Loan Receivable, ESOP		$ 1,500,000			$ 1.80	$ 266,000
Stock Issued During Period, Shares, Employee Stock Purchase Plans	150,358	150,358
Shares Issued, Price Per Share	$ 10	$ 10
Defined Benefit Plan, Unfunded Pension Liability							$ 218,000
Defined Benefit Plan, Funded Percentage							95.00%
Pension Cost (Reversal of Cost)				$ 202,000	215,000
Multiemployer Plans, Pension [Member] | Pentegra Defined Benefit Plan [Member]
Multiemploye Plan, Contributions by Employer				$ 110,000	$ 130,000
Multiemployer Plan, Contributions by Employer, Percentage				5.00%	5.00%
Treasury Stock [Member]
Stock Issued During Period, Shares, Employee Stock Ownership Plan			13,948			13,948
Employee Stock Ownership Plan (ESOP), Compensation Expense				$ 77,000	$ 59,000
Deferred Profit Sharing [Member]
Deferred Compensation Arrangement with Individual, Compensation Expense				$ 381,000	$ 251,000
Profit Sharing Plan [Member]
Defined Contribution Plan, Vesting Period				6 years
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay				4.00%
Profit Sharing Plan, First 3% of Employee Contribution [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Match				100.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay				3.00%
Profit Sharing Plan, Next 2% of Employee Contribution [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Match				50.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay				2.00%