Note 5 - Components of Pension and Other Post-employment Benefit (OPEB) Plans Net Periodic Benefit Costs - Components of Net Periodic Benefit (Credit) Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Pension Settlement	$ 0	$ 0	$ 22	$ 0
Pension Plan [Member]
Service Cost	278	296	836	887
Interest Cost	3,563	5,044	10,667	15,132
Expected Return on Plan Assets	(10,542)	(10,455)	(31,626)	(31,365)
Amortization of Prior Service Credits	0	0	0	0
Amortization of Actuarial Loss	1,368	1,730	4,102	5,191
Pension Settlement	0	0	22	0
Net Periodic Benefit (Credit) Cost	(5,333)	(3,385)	(15,999)	(10,155)
Other Postretirement Benefits Plan [Member]
Service Cost	0	0	0	0
Interest Cost	1,819	3,199	5,456	9,597
Expected Return on Plan Assets	0	0	0	0
Amortization of Prior Service Credits	(602)	(601)	(1,804)	(1,804)
Amortization of Actuarial Loss	1,629	2,319	4,887	6,958
Pension Settlement	0	0	0	0
Net Periodic Benefit (Credit) Cost	$ 2,846	$ 4,917	$ 8,539	$ 14,751