Note 6 - Defined Benefit Plan - Defined Benefit Plan Activity (Details) - Pension Plan [Member] - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Service cost	$ 651	$ 519
Interest cost	600	558
Expected return on plan assets	(1,200)	(822)
Amortization of prior service cost	(81)	(81)
Recognized net actuarial loss	438	405
Net periodic benefit cost	$ 408	$ 579