Note 9 - Retirement Plans (Details Textual)	Dec. 14, 2020 USD ($)
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 73,000,000

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Name:	us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration