Note 11 - Equity-based Compensation - Deferred Stock Unit Activity (Details) - $ / shares	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock Awards, Outstanding (in shares)	1,034,964	1,143,205	1,428,878
Weighted average award date fair value (in dollars per share)	$ 23.20	$ 23.26	$ 21.53
Stock Awards, Outstanding (in shares)	1,043,607	1,034,964	1,143,205
Weighted average award date fair value (in dollars per share)	$ 22.40	$ 23.20	$ 23.26
Deferred Stock Units [Member]
Stock Awards, Outstanding (in shares)	253,340	287,350	269,977
Weighted average award date fair value (in dollars per share)	$ 20.71	$ 20.80	$ 20.14
Awards, grants during period (in shares)	70,426	50,174	45,681
Weighted average award date fair value, award granted (in dollars per share)	$ 14.59	$ 19.64	$ 23.72
Awards, distributed during period (in shares)	(59,297)	(84,184)	(28,308)
Weighted average award date fair value, award distributed (in dollars per share)	$ 21.66	$ 20.38	$ 19.22
Stock Awards, Outstanding (in shares)	264,469	253,340	287,350
Weighted average award date fair value (in dollars per share)	$ 18.87	$ 20.71	$ 20.80

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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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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