Note 7 - Employee Benefit Plans - Allocation of Recognized Period Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Allocation of recognized period costs	$ 2,732	$ 2,268	$ 8,642	$ 7,825
Cost of Sales [Member]
Allocation of recognized period costs	745	787	2,404	2,768
Research and Development Expense [Member]
Allocation of recognized period costs	1,062	725	3,681	2,449
Selling, General and Administrative Expenses [Member]
Allocation of recognized period costs	$ 925	$ 756	$ 2,557	$ 2,608