Note 4 - Loans and Allowance for Credit Losses (Details Textual)	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Certain Loans Acquired in Transfer Accounted for as Debt Securities, Accretable Yield	$ 9,592	$ 82,869	$ 175,342
Impaired Financing Receivable, Interest Income, Cash Basis Method	10,000	5,000
Impaired Financing Receivable, Recorded Investment	$ 1,497,491	4,893,512
Financing Receivable, Modifications, Number of Contracts	0
Loans and Leases Receivable, Related Parties	$ 82,016	83,604
Troubled Debt Restructurings [Member]
Impaired Financing Receivable, Recorded Investment	500,000	2,400,000
Financing Receivables, Impaired, Troubled Debt Restructuring, Decreased	$ 1,900,000
Financing Receivable, Modifications, Number of Contracts Paid-off	3
Proceeds from Impaired Loans, Principal Payment	$ 1,700,000
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down	200,000
One- to Four-family Loan [Member] | Residential Portfolio Segment [Member]
Impaired Financing Receivable, Recorded Investment	1,130,849	$ 2,604,185
Financing Receivable, Modifications, Number of Contracts		2
Financing Receivable, Modifications, Recorded Investment		$ 79,200
Twin Oaks [Member]
Business Combination, Acquired Receivables, Gross Contractual Amount				$ 28,638,000
Business Combination, Acquired Receivable, Fair Value				28,472,000
Twin Oaks [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Business Combination, Acquired Receivables, Gross Contractual Amount	$ 468,000	$ 1,108,000
Loans Receivable [Member] | Twin Oaks [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Assets				31,831,910
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance				407,000
Certain Loans Acquired in Transfer, Accretable Yield				573,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net				166,000
Certain Loans Acquired in Transfer Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition				3,194,000
Certain Loans Acquired in Transfer Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition				1,324,000
Certain Loans Acquired in Transfer Accounted for as Debt Securities, Carrying Amount, Net				1,870,000
Certain Loans Acquired in Transfer Accounted for as Debt Securities, Accretable Yield				362,000
Certain Loans Acquired in Transfer, Nonaccretable Difference				1,508,000
Loans Receivable [Member] | Twin Oaks [Member] | Estimate of Fair Value Measurement [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Assets				$ 29,795,910