Pension and Postretirement Plans (Total Benefit/Cost) (Details 1) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Cost (Benefit)	$ 4,317	$ 4,591	$ 9,257	$ 9,505
Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	4,317	4,591	9,257	9,505
Interest cost	11,844	11,979	23,099	23,965
Expected return on assets	(32,796)	(30,403)	(65,282)	(60,740)
Amortization of prior service cost (credit)	36	43	78	86
Recognized actuarial loss (gain)	(2,974)	(1,039)	(4,020)	(2,333)
Net Periodic Benefit	(19,573)	(14,829)	(36,868)	(29,517)
Curtailment gain	0	0	(806)	0
Net Periodic Cost (Benefit)	(19,573)	(14,829)	(37,674)	(29,517)
Supplemental Executive Retirement Plan (SERP) [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	204	215	409	429
Interest cost	966	1,058	1,932	2,116
Amortization of prior service cost (credit)	78	114	156	228
Recognized actuarial loss (gain)	601	443	1,202	887
Net Periodic Cost (Benefit)	1,849	1,830	3,699	3,660
Other Postretirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	268	257	536	514
Interest cost	169	194	339	389
Amortization of prior service cost (credit)	(44)	(37)	(88)	(74)
Recognized actuarial loss (gain)	(921)	(972)	(1,843)	(1,945)
Net Periodic Cost (Benefit)	$ (528)	$ (558)	$ (1,056)	$ (1,116)