Pension and Other Post-Retirement Benefit Plans (Net Periodic Benefit Costs) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pension Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	8,775	8,968	17,550	17,936
Expected return on plan assets	(10,930)	(10,264)	(21,859)	(20,528)
Amortization of prior service cost	0	0	0	0
Amortization of net loss	1,937	3,368	3,874	6,736
Net periodic benefit (income) cost	(218)	2,072	(435)	4,144
Post-Retirement Healthcare Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	39	31	78	62
Interest cost	36	42	72	84
Expected return on plan assets	0	0	0	0
Amortization of prior service cost	(13)	(26)	(26)	(52)
Amortization of net loss	71	40	142	80
Net periodic benefit (income) cost	$ 133	$ 87	$ 266	$ 174