Pension and Other Post-Retirement Benefit Plans (Net Periodic Benefit Costs) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Pension Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 0	$ 0
Interest cost	8,775	8,968
Expected return on plan assets	(10,930)	(10,264)
Amortization of prior service cost	0	0
Amortization of net loss	1,937	3,368
Net periodic benefit (income) cost	(218)	2,072
Post-Retirement Healthcare Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	39	31
Interest cost	36	42
Expected return on plan assets	0	0
Amortization of prior service cost	(13)	(26)
Amortization of net loss	71	40
Net periodic benefit (income) cost	$ 133	$ 87