Note 11 - Stock-based Compensation (Details Textual) - USD ($)	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allocated Share-based Compensation Expense	$ 5,900,000	$ 4,800,000	$ 4,300,000
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	$ 2,300,000	$ 1,700,000	$ 1,300,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	0	0	0
Omnibus Plan 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	1,100,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	489,320
Omnibus Plan 2014 [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Omnibus Plan 2014 [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	10 years
Phantom Stock Plan [Member]
Allocated Share-based Compensation Expense	$ 700,000	$ 200,000	$ 17,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value	$ 45,000	$ 12,000	$ 35,000
Phantom Stock Plan [Member] \| Annually [Member] \| Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	20.00%
Phantom Stock Plan [Member] \| Vested Upon Change in Control [Member] \| Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	100.00%
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	337,175	318,120	266,895
Restricted Stock Units (RSUs) [Member] \| Omnibus Plan 2014 [Member]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$ 6,500,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	3 years 36 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value	$ 4,900,000	$ 4,900,000	$ 4,400,000
Phantom Share Units (PSUs) [Member] \| Phantom Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period	1 year

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
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Unrecognized cost of unvested share-based compensation awards.

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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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The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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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 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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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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

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