Note 8 - Employee Retirement Plans (Details Textual) $ in Millions	3 Months Ended
Mar. 31, 2022 USD ($)
Other Postretirement Benefits Plan [Member] \| UNITED STATES
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 30

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

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