Note 15 - Stock-based Compensation (Details Textual) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)	38,450	58,993	36,984
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 0.8
Stock or Unit Option Plan Expense	0.2	$ 0.2	$ 0.3
Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount	$ 0.3
Share-based Payment Arrangement, Option [Member]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)	2 years 6 months
Restricted Stock and Restricted Stock Units [Member]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)	3 years 2 months 12 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)	129,082	102,953
Share-based Payment Arrangement, Expense	$ 1.6	$ 1.4	1.1
Share-based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount	$ 3.7	$ 3.4	$ 2.8
Key Personnel [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)	38,450	58,993	36,984
Key Personnel [Member] \| Share-based Payment Arrangement, Option [Member] \| Share-based Payment Arrangement, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	20.00%
Key Personnel [Member] \| Share-based Payment Arrangement, Option [Member] \| Share-based Payment Arrangement, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	20.00%
Key Personnel [Member] \| Share-based Payment Arrangement, Option [Member] \| Share-based Payment Arrangement, Tranche Four [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	20.00%
Key Personnel [Member] \| Share-based Payment Arrangement, Option [Member] \| Share-based Payment Arrangement, Tranche Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	20.00%
Key Personnel [Member] \| Share-based Payment Arrangement, Option [Member] \| Share-based Payment Arrangement, Tranche Five [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	20.00%
Employees [Member] \| Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period (Year)	5 years
Employees [Member] \| Restricted Stock Units (RSUs) [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)	2 years
Employees [Member] \| Restricted Stock Units (RSUs) [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)	5 years
Director [Member] \| Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period (Year)	2 years
Employees and Directors [Member] \| Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)	129,082	102,953	79,439
Employees and Directors [Member] \| Restricted Stock Units (RSUs) [Member] \| Share-based Payment Arrangement, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)	5 years	5 years	5 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)	105,294	91,268	68,430
Employees and Directors [Member] \| Restricted Stock Units (RSUs) [Member] \| Share-based Payment Arrangement, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)	2 years	2 years	2 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)	23,788	11,685	11,009
A 2017 Long Term Incentive Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)	1,200,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized (in shares)	600,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares)	723,762

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Amount of noncash expense for option under share-based payment arrangement.

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