Pension and Postretirement Plans (Total Benefit/Cost) (Details 1) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Cost (Benefit)	$ (14,829)	$ (12,266)	$ (29,517)	$ (24,325)
Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	4,591	5,040	9,505	10,382
Interest cost	11,979	12,845	23,965	25,918
Expected return on assets	(30,403)	(30,226)	(60,740)	(60,774)
Amortization of prior service cost (credit)	43	75	86	149
Recognized actuarial loss (gain)	(1,039)	0	(2,333)	0
Net Periodic Cost (Benefit)	(14,829)	(12,266)	(29,517)	(24,325)
Supplemental Executive Retirement Plan (SERP) [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	215	246	429	492
Interest cost	1,058	1,096	2,116	2,192
Amortization of prior service cost (credit)	114	114	228	228
Recognized actuarial loss (gain)	443	665	887	1,330
Net Periodic Cost (Benefit)	1,830	2,121	3,660	4,242
Other Postretirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	257	347	514	693
Interest cost	194	307	389	615
Amortization of prior service cost (credit)	(37)	(84)	(74)	(168)
Recognized actuarial loss (gain)	(972)	(376)	(1,945)	(751)
Net Periodic Cost (Benefit)	$ (558)	$ 194	$ (1,116)	$ 389