Note 15 - Pension and Other Postretirement Benefit Plans (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	$ (22)	$ (0)	$ (0)
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax	16	0	0
Other Comprehensive Income (Loss), Defined Benefit Plan, Adjustment for Settlement or Curtailment Gain (Loss), Tax	$ (6)	0	0
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost Assumed Time Horizon (Year)	20 years
Defined Benefit Plan, Plan Assets, Amount, Ending Balance	$ 733,966	740,978
Defined Benefit Plan, Expected Future Benefit Payment, Year One	$ 11,504
United States Equity Securities [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	13.00%
Non U.S. Equity Securities [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	8.50%
Global Equity Securities [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	3.50%
Fixed Equity Securities [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	75.00%
Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	$ (22)	(0)	(0)
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Remeasurement due to Settlement	(1,009)
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax	766
Other Comprehensive Income (Loss), Defined Benefit Plan, Adjustment for Settlement or Curtailment Gain (Loss), Tax	265
Defined Benefit Plan, Plan Assets, Amount, Ending Balance	733,966	740,978	668,481
Defined Benefit Plan, Expected Future Benefit Payment, Year One	43,826
Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment, Year One	1,974
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0	0	(0)
Defined Benefit Plan, Plan Assets, Amount, Ending Balance	0	$ 0	$ 0
Defined Benefit Plan, Expected Future Benefit Payment, Year One	23,638
Commodity Contract [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	$ 22