Pension and Other Post-Retirement Benefit Plans (Funded Status) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pension Plans [Member]
Change in benefit obligation [Roll Forward]
Service cost	$ 0	$ 0
Interest cost	7,825	7,284
Change in plan assets [Roll Forward]
Employer contributions	579
Post-Retirement Healthcare Plans [Member]
Change in benefit obligation [Roll Forward]
Service cost	27	30
Interest cost	$ 37	$ 32