Pension and Postretirement Plans (Total Benefit/Cost) (Details 1) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Special separation benefit expense			$ 0	$ 932
Net Periodic Cost (Benefit)	$ 4,473	$ 4,591	13,730	14,096
Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	4,473	4,591	13,730	14,096
Interest cost	11,844	11,980	34,943	35,945
Expected return on assets	(31,969)	(30,338)	(97,251)	(91,078)
Amortization of prior service cost (credit)	36	42	114	128
Recognized actuarial loss (gain)	(2,974)	(1,039)	(6,994)	(3,372)
Net Periodic Benefit	(18,590)	(14,764)	(55,458)	(44,281)
Curtailment gain	0	0	(806)	0
Special separation benefit expense	0	932	0	932
Net Periodic Cost (Benefit)	(18,590)	(13,832)	(56,264)	(43,349)
Supplemental Executive Retirement Plan (SERP) [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	205	214	614	643
Interest cost	967	1,059	2,899	3,175
Amortization of prior service cost (credit)	77	114	233	342
Recognized actuarial loss (gain)	600	444	1,802	1,331
Net Periodic Cost (Benefit)	1,849	1,831	5,548	5,491
Other Postretirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	267	257	803	771
Interest cost	170	195	509	584
Amortization of prior service cost (credit)	(44)	(38)	(132)	(112)
Recognized actuarial loss (gain)	(921)	(972)	(2,764)	(2,917)
Net Periodic Cost (Benefit)	$ (528)	$ (558)	$ (1,584)	$ (1,674)