Note 13 - Employee Benefit Plans (Details Textual) $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares
Deferred Compensation Arrangement with Individual, Recorded Liability	$ 0	$ 0
Deferred Compensation Arrangement with Individual, Compensation Expense	0	11	$ 60
Stop-loss Insurance Liability for Individual Claims	150
Stop-loss Insurance Liability for Aggregate Claims	4,200
Other Postretirement Benefits Cost (Reversal of Cost)	$ 3,720	$ 3,500	$ 3,480
Common Stock, Shares Held in Employee Trust, Shares \| shares	366,969	387,935	410,384
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross \| shares	0
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 423	$ 84	$ 434
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options	$ 65
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 29 days
Restricted Stock [Member]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options	$ 927
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 346 days
2012 Omnibus Incentive Compensation Plan [Member] \| Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant \| shares	600,000
Share-based Compensation Arrangement By Share-based Payment Award, Maximum Exercise Period	10 years
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
2012 Omnibus Incentive Compensation Plan [Member] \| Employee Stock Option [Member] \| Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	25.00%
Supplemental Employee Retirement Plan [Member]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	35.00%
Defined Benefit Plan, Employee Contribution, Age	62
Directors' Plan [Member]
Defined Benefit Plan, Employee Contribution, Age	70
Defined Contribution Plan, Maximum Employee Contribution as Percentage of Base Salary	100.00%
401 (k) Savings Plan [Member]
Defined Benefit Plan, Employer Matching Contributions	$ 1,060	$ 1,180	$ 1,500

Represents the employee contribution age for defined benefit plan.

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Amount of employer matching contributions to the plan.

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Represents the maximum percentage of base salary the employee contribution.

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- Definition

Period from grant date that an equity-based award can be exercised, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

Amount of stop-loss insurance coverage for aggregate claims.

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Amount of stop-loss insurance coverage for individual claims.

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- Definition

Number of common stock held in a trust that has been set up specifically to accumulate stock for the sole purpose of distribution to participating employees but not yet earned.

+ References

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The compensation expense recognized during the period pertaining to the deferred compensation arrangement.

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- Definition

The carrying amount of the liability as of the balance sheet date to an individual under a deferred compensation arrangement. This amount may be the result of periodic accruals made over the period of active employment, or reflect termination benefits resulting contractual terms or a death benefit.

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- Definition

Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

+ References

No definition available.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Unrecognized cost of unvested options awarded to employees as compensation.

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- Definition

Amount of cost (reversal of cost) for other postretirement benefits. Excludes pension benefits.

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No definition available.

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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.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Gross number of share options (or share units) granted during the period.

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Percentage of vesting of share-based compensation awards.

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