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
	Mar. 31, 2021	Mar. 31, 2020
Pension Plan [Member]
Service Cost	$ 279	$ 296
Interest Cost	3,550	5,044
Expected Return on Plan Assets	(10,542)	(10,455)
Amortization of Prior Service Credits	0	0
Amortization of Actuarial Loss	1,367	1,730
Net Periodic Benefit (Credit) Cost	(5,346)	(3,385)
Other Postretirement Benefits Plan [Member]
Service Cost	0	0
Interest Cost	1,818	3,199
Expected Return on Plan Assets	0	0
Amortization of Prior Service Credits	(601)	(601)
Amortization of Actuarial Loss	1,629	2,319
Net Periodic Benefit (Credit) Cost	$ 2,846	$ 4,917