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Note 11 - Pension Plan and Other Postretirement Benefits - Pension Fund Assets Measured at Fair Value (Details) - Pension Plan [Member] - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value of Plan Assets	$ 329,781	$ 269,783	$ 285,319
Fair Value, Inputs, Level 1 [Member]
Fair Value of Plan Assets	320,241	258,307
Fair Value, Inputs, Level 1 [Member] | Mixed Equities Fund [Member]
Fair Value of Plan Assets	67,184	0
Fair Value, Inputs, Level 1 [Member] | Large Capitalization Equity Securities [Member]
Fair Value of Plan Assets	37,357	47,198
Fair Value, Inputs, Level 1 [Member] | International Equity Securities [Member]
Fair Value of Plan Assets	30,653	45,912
Fair Value, Inputs, Level 1 [Member] | Small and Mid Capitalization Equity Securities [Member]
Fair Value of Plan Assets	13,447	17,971
Fair Value, Inputs, Level 1 [Member] | SEI Dynamic Asset Allocation Fund [Member]
Fair Value of Plan Assets	10,168	10,929
Fair Value, Inputs, Level 1 [Member] | Emerging Markets Equity Funds [Member]
Fair Value of Plan Assets	13,792	9,197
Fair Value, Inputs, Level 1 [Member] | Fixed Income Securities [Member]
Fair Value of Plan Assets	147,639	127,098
Fair Value, Inputs, Level 1 [Member] | Cash Management Money Market Fund [Member]
Fair Value of Plan Assets	$ 1	$ 2

X

- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

+ References

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-Publisher FASB
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