Note 6 - Defined Benefit Plan - Defined Benefit Plan Activity (Details) - Pension Plan [Member] - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Service cost	$ 600	$ 651
Interest cost	663	600
Expected return on plan assets	(1,095)	(1,200)
Amortization of prior service cost	(81)	(81)
Recognized net actuarial loss	474	438
Net periodic benefit cost	$ 561	$ 408