Note 11 - Equity-based Compensation (Details Textual) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Share-based Payment Arrangement, Expense, Tax Benefit	$ 5.2
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost	3.1
Restricted Stock Units (RSUs) [Member]
Share-based Payment Arrangement, Expense	2.5	$ 1.8
Share-based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount	$ 18.6
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)	1 year 6 months
Stock Appreciation Rights (SARs) [Member]
Share-based Payment Arrangement, Expense	$ 0.7	1.2
Share-based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount	$ 5.7
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)	1 year 4 months 24 days
Selling, General and Administrative Expenses [Member]
Share-based Payment Arrangement, Expense	$ 3.2	$ 3.0
The 2015 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares)	151,367

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

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