Note 10 - Employee Benefit Plans - Components of Net Periodic Pension Cost and Assumed Discount Rate (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Service cost	$ 55	$ 58	$ 123	$ 116
Interest cost	90	93	179	186
Amortization of prior service cost	55	57	114	114
Amortization of losses	16	8	28	15
Net periodic cost	$ 216	$ 216	$ 444	$ 431