Note 17 - Retirement Plans - Benefit Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plan [Member] | UNITED STATES
Benefit obligation, beginning of year	$ 57,718	$ 58,556
Service cost
Interest cost	2,214	2,390	2,430
Actuarial loss	2,676	427
Benefits paid	(3,422)	(3,655)
Benefit obligation, end of year	59,186	57,718	58,556
Pension Plan [Member] | Foreign Plan [Member]
Benefit obligation, beginning of year	25,002	22,748
Service cost	941	742	778
Interest cost	732	740	589
Actuarial loss	798	3,255
Benefits paid	(725)	(700)
Currency translation effect	2,675	(1,783)
Benefit obligation, end of year	29,423	25,002	22,748
Supplemental Employee Retirement Plan [Member]
Benefit obligation, beginning of year	1,209	1,800
Service cost
Interest cost	9	18	24
Actuarial loss
Benefits paid	(609)	(609)
Benefit obligation, end of year	$ 609	$ 1,209	$ 1,800