Pension and Other Post-Retirement Benefit Plans (Net Periodic Benefit Costs) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Pension Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	7,284	8,396	21,852	25,946
Expected return on plan assets	(10,523)	(10,520)	(31,569)	(32,379)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment	0	(12,923)	0	(12,923)
Amortization of prior service cost	0	0	0	0
Amortization of net (gain) loss	887	1,944	2,661	5,819
Net periodic benefit cost (income)	(2,352)	12,743	(7,056)	12,309
Post-Retirement Healthcare Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	30	39	90	117
Interest cost	32	36	96	108
Expected return on plan assets	0	0	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment	0	0	0	0
Amortization of prior service cost	0	(13)	0	(39)
Amortization of net (gain) loss	55	71	165	213
Net periodic benefit cost (income)	$ 117	$ 133	$ 351	$ 399