Pension and Other Postretirement Benefits - Net Periodic Benefit Cost and Changes in Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service Cost	$ 316	$ 1,164	$ 632	$ 2,338
Interest Cost	1,094	1,486	2,184	3,255
Expected Return on Plan Assets	(2,093)	(1,761)	(4,175)	(3,720)
Settlement Loss	0	0	0	22,667
Actuarial Loss Amortization	857	615	1,712	1,662
Prior Service (Credit) Cost Amortization	3	(41)	5	(81)
Net Periodic Benefit Cost	177	1,463	358	26,121
Other Postretirement Benefit Plans Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service Cost	2	1	3	3
Interest Cost	10	26	21	52
Expected Return on Plan Assets	0	0	0	0
Settlement Loss	0	0	0	0
Actuarial Loss Amortization	0	16	0	31
Prior Service (Credit) Cost Amortization	0	0	0	0
Net Periodic Benefit Cost	$ 12	$ 43	$ 24	$ 86