Pension and Postretirement Plans (Total Benefit/Cost) (Details 1) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5,602	$ 5,783
Net Periodic Cost (Benefit)	(24,501)	(13,784)
Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	5,602	5,783
Interest cost	6,654	8,169
Expected return on assets	(34,576)	(28,444)
Amortization of prior service cost (credit)	711	708
Recognized actuarial loss (gain)	(2,892)	0
Net Periodic Cost (Benefit)	(24,501)	(13,784)
Supplemental Executive Retirement Plan (SERP) [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	255	238
Interest cost	736	919
Amortization of prior service cost (credit)	83	83
Recognized actuarial loss (gain)	1,482	1,317
Net Periodic Cost (Benefit)	2,556	2,557
Other Postretirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	36	62
Amortization of prior service cost (credit)	(2)	(120)
Recognized actuarial loss (gain)	(1,019)	(1,097)
Net Periodic Cost (Benefit)	$ (985)	$ (1,155)