Note 5 - Defined Benefit Plan - Defined Benefit Plan Activity (Details) - Pension Plan [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Service cost	$ 361	$ 270	$ 1,083	$ 810
Interest cost	184	205	552	615
Expected return on plan assets	(555)	(420)	(1,665)	(1,260)
Amortization of prior service cost	(3)	(27)	(9)	(81)
Recognized net actuarial loss	208	177	624	531
Net periodic benefit cost	$ 195	$ 205	$ 585	$ 615