Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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The amount of the remaining liabilities were reversed associated the modification of the plan.

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Shares matched.

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Note 10 - Equity Plans (Details Textual) - USD ($)					3 Months Ended	12 Months Ended
Note 10 - Equity Plans (Details Textual) - USD ($)	Mar. 13, 2017	Jul. 01, 2016	May 01, 2016	Mar. 01, 2015	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement By Share-based Payment Award, Equity Instruments Other Than Options Converted into Shares, Intrinsic Value						$ 0	$ 0	$ 0
Senior Management Compensation Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Minimum Number of Shares Per Employee		750
Share-based Compensation Arrangement by Share-based Payment Award, Matching Purchase Requirement		500
Share-based Compensation Arrangement by Share-based Payment Award, Award Match		250
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period						73,021
Restricted Stock Units (RSUs) [Member] \| Supplemental Employee Retirement Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period						26,837	51,075	47,639
Restricted Stock Units (RSUs) [Member] \| Senior Management Stock Incentive Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		5 years
Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Participant's Base Salary		10.00%
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Amount Per Employee		$ 17,500
Restricted Stock Units (RSUs) [Member] \| Senior Management Compensation Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Plan Modification, Remaining Liability Reversed		1,000,000
Restricted Stock Units (RSUs) [Member] \| Senior Management Compensation Program [Member] \| Five Year Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested		25,000
Restricted Stock Units (RSUs) [Member] \| Senior Management Compensation Program [Member] \| Ten Year Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested		50,000
Restricted Stock Units (RSUs) [Member] \| Senior Management Compensation Program [Member] \| Fifteen Year Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested		75,000
Restricted Stock Units (RSUs) [Member] \| Senior Management Compensation Program [Member] \| Twenty Five Year Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested		100,000
Restricted Stock Units (RSUs) [Member] \| Senior Management Compensation Program [Member] \| Twenty Year Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested		$ 100,000
Restricted Stock Units (RSUs) [Member] \| Non-Employee Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	3,501		3,094	4,639
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period						1 year
Restricted Stock Units (RSUs) [Member] \| Executive Vice President and Chief Operating Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period					10,573
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period					5 years
Match [Member] \| Senior Management Compensation Program [Member]
Shares Matched							2,500	9,000
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant						1,000,000
Share Price	$ 19.99		$ 22.62	$ 15.09