Pension and Postretirement Plans (Total Benefit/Cost) (Details 1) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5,804	$ 4,963	$ 11,587	$ 10,184
Special separation benefit expense			6,014
Net Periodic Cost (Benefit)			(21,409)	(19,763)
Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	5,804	4,963	11,587	10,184
Interest cost	8,140	11,743	16,309	23,335
Expected return on assets	(28,290)	(30,285)	(56,734)	(61,123)
Amortization of prior service cost (credit)	707	825	1,415	1,234
Recognized actuarial loss (gain)	0	37	0	0
Net Periodic Cost (Benefit)	(13,639)	(12,717)	(27,423)	(26,370)
Special separation benefit expense	6,014	6,607	6,014	6,607
Net Periodic Cost (Benefit)	(7,625)	(6,110)	(21,409)	(19,763)
Supplemental Executive Retirement Plan (SERP) [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	239	215	477	429
Interest cost	920	1,079	1,839	2,157
Amortization of prior service cost (credit)	82	84	165	169
Recognized actuarial loss (gain)	1,317	578	2,634	1,157
Net Periodic Cost (Benefit)	2,558	1,956	5,115	3,912
Other Postretirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	22	72	84	144
Amortization of prior service cost (credit)	(121)	(1,840)	(241)	(3,681)
Recognized actuarial loss (gain)	(927)	(1,090)	(2,024)	(2,180)
Net Periodic Cost (Benefit)	$ (1,026)	$ (2,858)	$ (2,181)	$ (5,717)