Note 11 - Employee Benefit Plans (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	80.00%
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 3,300	$ 0	$ 4,800