Note 9 - Employee Retirement Plans - Amounts Recognized In Other Comprehensive Income Loss (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan [Member]
Net (gain) loss	$ (568)	$ 2,612	$ (3,441)
Settlement recognized	0	(182)	(335)
Total recognized in other comprehensive (income) loss, before tax and net of tax	$ (568)	$ 2,430	(3,776)
Other Pension Plan [Member]
Net (gain) loss			229
Total recognized in other comprehensive (income) loss, before tax and net of tax			1,536
Amortization of prior service (cost) credit			1,861
Amortization of net (loss) gain			$ (554)

Amount, before tax, of reclassification adjustment from accumulated other comprehensive (income) loss for prior service cost (credit) of defined benefit plan.

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Amount, before tax, of increase (decrease) to other comprehensive income from settlement and curtailment gain (loss) of defined benefit plan.

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