Note 13 - Employee Retirement Benefit Plans (Details Textual) - USD ($)		1 Months Ended	12 Months Ended
	Oct. 11, 2016	Oct. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Jul. 01, 2018	Dec. 31, 2016	Dec. 31, 2014
Loan Receivable, ESOP		$ 1,500,000				$ 1,800,000	$ 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					$ 405,000
Defined Benefit Plan, Funded Percentage					91.00%
Pension Cost (Reversal of Cost)			$ 44,000	$ 202,000
Multiemployer Plans, Pension [Member] | Pentegra Defined Benefit Plan [Member]
Multiemploye Plan, Contributions by Employer			$ 82,000	$ 110,000
Multiemployer Plan, Contributions by Employer, Percentage			5.00%	5.00%
Treasury Stock [Member]
Employee Stock Ownership Plan (ESOP), Compensation Expense			$ 90,000	$ 84,000
Deferred Profit Sharing [Member]
Deferred Compensation Arrangement with Individual, Compensation Expense			$ 375,000	$ 381,000
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%