Note 15 - Employee Benefit Plan (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage	100.00%
Defined Contribution Plan, Cost	$ 1.7	$ 1.7	$ 1.7
Defined Contribution Plan, Maximum Defer Base Salary, Percent	85.00%
Defined Contribution Plan, Maximum Defer Bonus, Percent	100.00%
Deferred Compensation Liability, Current and Noncurrent, Total	$ 3.0	3.1
Payment to Acquire Life Insurance Policy, Investing Activities	2.9	$ 2.1
Gain (Loss) On Death Benefit	$ 4.0