Note 15 - Pension and Other Postretirement Benefit Plans - Schedule of Expected Benefit Payments (Details) $ in Thousands	Dec. 31, 2020 USD ($)
2021	$ 10,580
2022	10,392
2023	10,212
2024	10,151
2025	10,015
Year 2026-2030	50,445
Pension Plan [Member]
2021	44,391
2022	43,639
2023	43,112
2024	42,755
2025	41,291
Year 2026-2030	196,850
Other Postretirement Benefits Plan [Member]
2021	26,073
2022	25,250
2023	24,455
2024	23,581
2025	23,249
Year 2026-2030	$ 110,456

Amount of benefit for defined benefit plan expected to be paid in five fiscal years after fifth fiscal year following current fiscal year.

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

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Amount of benefit for defined benefit plan expected to be paid in next fiscal year following current fiscal year.

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Amount of benefit for defined benefit plan expected to be paid in fifth fiscal year following current fiscal year.

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Amount of benefit for defined benefit plan expected to be paid in fourth fiscal year following current fiscal year.

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Amount of benefit for defined benefit plan expected to be paid in second fiscal year following current fiscal year.

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