Note 13 - Retirement Benefit Plans - Weighted-average Assumptions Used (Details)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Postretirement Health Coverage [Member]
Discount rate, benefit obligations	2.07%	3.06%
Rate of compensation increase, benefit obligations	0.00%	0.00%
Discount rate, net periodic benefit costs	3.06%	3.95%	3.26%
Expected long-term rate of return on plan assets, net periodic benefit costs	0.00%	0.00%	0.00%
Rate of compensation increase, net periodic benefit costs	0.00%	0.00%	0.00%
UNITED STATES \| Pension Plan [Member]
Discount rate, net periodic benefit costs	3.01%	3.95%	3.28%
Expected long-term rate of return on plan assets, net periodic benefit costs	0.00%	0.00%	0.00%
Rate of compensation increase, net periodic benefit costs	0.00%	0.00%	0.00%
UNITED STATES \| Nonqualified Plan [Member]
Discount rate, benefit obligations	2.06%	3.01%
Rate of compensation increase, benefit obligations	0.00%	0.00%
Foreign Plan [Member] \| Pension Plan [Member]
Discount rate, benefit obligations	1.05%	1.42%
Rate of compensation increase, benefit obligations	0.00%	0.00%
Discount rate, net periodic benefit costs	1.42%	1.92%	2.08%
Expected long-term rate of return on plan assets, net periodic benefit costs	3.30%	3.80%	3.80%
Rate of compensation increase, net periodic benefit costs	0.00%	0.00%	3.50%

Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

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- Definition

Weighted average rate increase of compensation, used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

+ References

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- Definition

Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan.

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- Definition

Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(3)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2919-114920

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- Definition

Weighted average rate of compensation increase used to determine net periodic benefit cost of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

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