Note 5 - Defined Benefit Plan - Defined Benefit Plan Activity (Details) - Pension Plan [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Service cost	$ 361	$ 270	$ 722	$ 540
Interest cost	184	205	368	410
Expected return on plan assets	(555)	(420)	(1,110)	(840)
Amortization of prior service cost	(3)	(27)	(6)	(54)
Recognized net actuarial loss	208	177	416	354
Net periodic benefit cost	$ 195	$ 205	$ 390	$ 410