Note 13 - Retirement Benefit Plans (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension and Other Postretirement Benefits Cost (Reversal of Cost), Total	$ 12,300	$ 13,700	$ 11,900
Defined Benefit Plan, Plan Assets, Amount, Ending Balance	$ 0
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	3.00%
Defined Contribution Plan, Minimum Service Period Required to be Eligible (Year)	1 year
Defined Contribution Plan, Cost	$ 7,200	9,800	8,100
Pension Plan [Member]
Defined Benefit Plan, Plan Assets, Amount, Ending Balance		15,000
UNITED STATES | Nonqualified Plan [Member]
Defined Benefit Plan, Plan Assets, Amount, Ending Balance	0	0	0
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	100
UNITED STATES | Retiree Plan [Member]
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	700
Foreign Plan [Member] | Pension Plan [Member]
Defined Benefit Plan, Plan Assets, Amount, Ending Balance	13,300	$ 12,200	10,800
Foreign Plan [Member] | UK Pension Plan [Member] | Pension Plan [Member]
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment			$ 100
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	400
Foreign Plan [Member] | German Pension Plan [Member] | Pension Plan [Member] | Maximum [Member]
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	100
Foreign Plan [Member] | Italian Pension Plan [Member] | Pension Plan [Member] | Maximum [Member]
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	$ 100