Pension and Postretirement Plans (Total Benefit/Cost) (Details 1) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Cost (Benefit)	$ (14,688)	$ (12,059)
Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	4,914	5,342
Interest cost	11,986	13,073
Expected return on assets	(30,337)	(30,548)
Amortization of prior service cost (credit)	43	74
Recognized actuarial loss (gain)	(1,294)	0
Net Periodic Cost (Benefit)	(14,688)	(12,059)
Supplemental Executive Retirement Plan (SERP) [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	214	246
Interest cost	1,058	1,096
Amortization of prior service cost (credit)	114	114
Recognized actuarial loss (gain)	444	665
Net Periodic Cost (Benefit)	1,830	2,121
Other Postretirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	257	346
Interest cost	195	308
Amortization of prior service cost (credit)	(37)	(84)
Recognized actuarial loss (gain)	(973)	(375)
Net Periodic Cost (Benefit)	$ (558)	$ 195