Pension and Other Post-Retirement Benefit Plans (Net Periodic Benefit Costs) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pension Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 0	$ 0
Interest cost	7,825	7,284
Expected return on plan assets	(9,477)	(10,523)
Amortization of net loss	3,882	887
Net periodic benefit cost (income)	2,230	(2,352)
Post-Retirement Healthcare Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	27	30
Interest cost	37	32
Expected return on plan assets	0	0
Amortization of net loss	43	55
Net periodic benefit cost (income)	$ 107	$ 117