Note 10 - Retirement Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Domestic Plan [Member]
Components of net periodic benefit cost
Interest cost	$ 553	$ 597	$ 1,661	$ 1,792
Expected return on plan assets	(677)	(662)	(2,031)	(1,986)
Recognized actuarial loss	199	194	599	582
Net periodic benefit cost	75	129	229	388
Foreign Plan [Member]
Components of net periodic benefit cost
Interest cost	192	186	545	560
Recognized actuarial loss	94	49	268	147
Net periodic benefit cost	532	420	1,510	1,265
Service cost	247	186	700	561
Amortization of prior service benefit	$ (1)	$ (1)	$ (3)	$ (3)