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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Pension Settlement	$ 22	$ 0	$ 22	$ 0
Pension Plan [Member]
Service Cost	279	295	558	591
Interest Cost	3,554	5,044	7,104	10,088
Expected Return on Plan Assets	(10,542)	(10,455)	(21,084)	(20,910)
Amortization of Prior Service Credits	0	0	0	0
Amortization of Actuarial Loss	1,367	1,731	2,734	3,461
Pension Settlement	22	0	22	0
Net Periodic Benefit (Credit) Cost	(5,320)	(3,385)	(10,666)	(6,770)
Other Postretirement Benefits Plan [Member]
Service Cost	0	0	0	0
Interest Cost	1,819	3,199	3,637	6,398
Expected Return on Plan Assets	0	0	0	0
Amortization of Prior Service Credits	(601)	(602)	(1,202)	(1,203)
Amortization of Actuarial Loss	1,629	2,320	3,258	4,639
Pension Settlement	0	0	0	0
Net Periodic Benefit (Credit) Cost	$ 2,847	$ 4,917	$ 5,693	$ 9,834