Pension and Postretirement Plans (Total Benefit/Cost) (Details 1) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Special separation benefit expense			$ 932	$ 0
Net Periodic Cost (Benefit)	$ (13,832)	$ (12,389)	(43,349)	(36,714)
Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	4,591	5,040	14,096	15,422
Interest cost	11,980	12,845	35,945	38,763
Expected return on assets	(30,338)	(30,348)	(91,078)	(91,122)
Amortization of prior service cost (credit)	42	74	128	223
Recognized actuarial loss (gain)	(1,039)	0	(3,372)	0
Net Periodic Benefit	(14,764)	(12,389)	(44,281)	(36,714)
Special separation benefit expense	932	0	932	0
Net Periodic Cost (Benefit)	(13,832)	(12,389)	(43,349)	(36,714)
Supplemental Executive Retirement Plan (SERP) [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	214	246	643	738
Interest cost	1,059	1,096	3,175	3,288
Amortization of prior service cost (credit)	114	114	342	342
Recognized actuarial loss (gain)	444	665	1,331	1,995
Net Periodic Cost (Benefit)	1,831	2,121	5,491	6,363
Other Postretirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	257	346	771	1,039
Interest cost	195	308	584	923
Amortization of prior service cost (credit)	(38)	(83)	(112)	(251)
Recognized actuarial loss (gain)	(972)	(376)	(2,917)	(1,127)
Net Periodic Cost (Benefit)	$ (558)	$ 195	$ (1,674)	$ 584