Note 6 - Stock-based Compensation - Stock-based Compensation Expense and Related Income Tax Benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock-based compensation expense, gross	$ 5,099	$ 4,019	$ 5,012
Income tax benefit at our statutory rate associated with stock-based compensation	(1,989)	(1,567)	(1,955)
Stock-based compensation expense, net	$ 3,110	$ 2,452	$ 3,057