Note 10 - Employment Benefit and Retirement Plans - Amounts Recognized in Statement of Financial Position (Details) - USD ($)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Director Retirement Plan [Member]
Accumulated post-retirement benefit obligation	$ (311,283)	$ (318,466)
Plan assets at fair value
Funded status	(311,283)	(318,466)
Actuarial loss	14,380	2,963
(Accrued) cost included in other liabilities	(296,903)	(315,503)
Director Retirement Plan [Member] \| Active Participants [Member]
Accumulated post-retirement benefit obligation	(116,478)	(113,270)
Director Retirement Plan [Member] \| Retired Participants Including Beneficiaries [Member]
Accumulated post-retirement benefit obligation	(194,805)	(205,196)
Postretirement Health Coverage [Member]
Accumulated post-retirement benefit obligation	(293,449)	(286,691)
Plan assets at fair value	0	0
Funded status	(293,449)	(286,691)
Actuarial loss	(118,270)	(125,028)
(Accrued) cost included in other liabilities	(411,719)	(411,719)
Postretirement Health Coverage [Member] \| Retirees [Member]
Accumulated post-retirement benefit obligation	(82,675)	(78,426)
Postretirement Health Coverage [Member] \| Active Employees Fully Eligible [Member]
Accumulated post-retirement benefit obligation	0	0
Postretirement Health Coverage [Member] \| Active Employees Not Yet Eligible [Member]
Accumulated post-retirement benefit obligation	$ (210,774)	$ (208,265)

Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

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Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

+ References

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- Definition

Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) status.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
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- Definition

Amount of accumulated benefit obligation for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
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- Definition

Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 45
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-URI http://asc.fasb.org/extlink&oid=64852052&loc=d3e1703-114919

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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- Definition

Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans, classified as noncurrent.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Topic 210
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