Note 12 - Pension and Postretirement Benefit Plans - Significant Weighted Average Assumptions Used in Measurement of Pension and Postretirement Benefit Obligations (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
UNITED STATES | Pension Plan [Member]
Benefit obligations:
Discount rate	2.43%	3.21%	4.22%
Net periodic benefit cost:
Discount rate	2.79%	3.41%	2.56%
Expected return on plan assets	5.00%	6.00%	6.00%
UNITED STATES | Other Postretirement Benefits Plan [Member]
Benefit obligations:
Discount rate	2.67%	3.37%
Net periodic benefit cost:
Discount rate	3.19%	4.08%
Foreign Plan [Member] | Pension Plan [Member]
Benefit obligations:
Discount rate	1.40%	1.72%	2.42%
Net periodic benefit cost:
Discount rate	2.10%	2.50%	2.54%
Rate of compensation increase	3.36%	3.28%	3.21%
Expected return on plan assets	4.45%	4.61%	4.66%
Foreign Plan [Member] | Other Postretirement Benefits Plan [Member]
Benefit obligations:
Discount rate	2.55%	3.10%	3.71%
Net periodic benefit cost:
Discount rate	3.15%	3.76%	3.42%
Initial health care cost trend rate	4.64%	4.22%	4.12%
Ultimate health care cost trend rate	5.13%	4.93%	5.10%
Year ultimate reached	2023	2023	2023