Note 8 - Income Taxes (Details Textual) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Percent, Total	47.70%	42.60%
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 8.7		$ 8.2
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total	0.9		$ 0.6
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, Total	0.3
Decrease in Unrecognized Tax Benefits is Reasonably Possible	$ 1.9
Earliest Tax Year [Member] \| Domestic Tax Authority [Member] \| Internal Revenue Service (IRS) [Member]
Income Tax Examination, Year under Examination	2013
Latest Tax Year [Member] \| Domestic Tax Authority [Member] \| Internal Revenue Service (IRS) [Member]
Income Tax Examination, Year under Examination	2014

Amount of decrease reasonably possible in the next twelve months for the unrecognized tax benefit.

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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Amount of expense for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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