Note 6 - Defined Benefit Plan - Defined Benefit Plan Activity (Details) - Pension Plan [Member] - USD ($) $ in Thousands	3 Months Ended	15 Months Ended
	Mar. 31, 2017	Mar. 31, 2018
Service cost	$ 173	$ 217
Interest cost	186	200
Expected return on plan assets	(274)	(400)
Amortization of prior service cost	(27)	(27)
Recognized net actuarial loss	135	146
Net periodic benefit cost	$ 193	$ 136