Note 4 - 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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Pension Plan [Member]
Service Cost	$ 295	$ 987	$ 591	$ 1,975
Interest Cost	5,044	6,275	10,088	12,551
Expected Return on Plan Assets	(10,455)	(10,114)	(20,910)	(20,229)
Amortization of Prior Service Credits	0	(92)	0	(183)
Amortization of Actuarial Loss	1,731	1,490	3,461	2,979
Net Periodic Benefit (Credit) Cost	(3,385)	(1,454)	(6,770)	(2,907)
Other Postretirement Benefits Plan [Member]
Service Cost	0	0	0	0
Interest Cost	3,199	4,580	6,398	9,160
Expected Return on Plan Assets	0	0	0	0
Amortization of Prior Service Credits	(602)	(601)	(1,203)	(1,203)
Amortization of Actuarial Loss	2,320	2,315	4,639	4,631
Net Periodic Benefit (Credit) Cost	$ 4,917	$ 6,294	$ 9,834	$ 12,588