Note 9 - Stockholders' Equity and Equity Compensation - Deferred Stock Unit Activity (Details)	9 Months Ended
Sep. 30, 2019 $ / shares shares
Stock Awards, Outstanding (in shares) \| shares	1,143,205
Weighted average award date fair value (in dollars per share) \| $ / shares	$ 23.26
Stock Awards, Outstanding (in shares) \| shares	1,174,799
Weighted average award date fair value (in dollars per share) \| $ / shares	$ 22.84
Deferred Stock Units [Member]
Stock Awards, Outstanding (in shares) \| shares	287,350
Weighted average award date fair value (in dollars per share) \| $ / shares	$ 20.80
Awards, grants during period (in shares) \| shares	47,767
Weighted average award date fair value, award granted (in dollars per share) \| $ / shares	$ 19.59
Awards, distributed during period (in shares) \| shares	(84,184)
Weighted average award date fair value, award distributed (in dollars per share) \| $ / shares	$ 20.38
Stock Awards, Outstanding (in shares) \| shares	250,933
Weighted average award date fair value (in dollars per share) \| $ / shares	$ 20.71

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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-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
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The weighted average fair value at grant date for nonvested equity-based awards issued 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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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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