Note 10 - Employment Benefit and Retirement Plans - Obligations and Funded Status (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Director Retirement Plan [Member]
Benefit obligation at beginning of year	$ 318,000	$ 335,000
Service cost	0	0
Interest cost	10,116	11,346
Actuarial loss (gain)	14,000	3,000
Benefits paid	(31,000)	(31,000)
Assumed liability	0	0
Benefit obligation at end of year	311,000	318,000
Employer contributions	31,000	31,000
Benefits paid	(31,000)	(31,000)
Fair value of plan assets at year end
Funded status	(311,283)	(318,466)
Actuarial loss (gain)	14,380	2,963
Net amount recognized	(297,000)	(315,000)
Postretirement Health Coverage [Member]
Benefit obligation at beginning of year	287,000	277,000
Service cost	6,319	6,537
Interest cost	8,993	11,363
Actuarial loss (gain)	(6,000)	(5,000)
Benefits paid	(8,000)	(8,000)
Benefit obligation at end of year	293,000	287,000
Employer contributions	4,000	3,000
Benefits paid	(9,000)	(8,000)
Fair value of plan assets at year end	0	0
Funded status	(293,449)	(286,691)
Actuarial loss (gain)	(118,270)	(125,028)
Net amount recognized	(412,000)	(412,000)
Plan amendments
Retiree contributions	5,000	5,000
Retiree contributions	$ 5,000	$ 5,000