Pension and Other Post-Retirement Benefit Plans (Cash Flows) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 5,414	$ 22,220
Estimated future employer contributions	10,900
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2017	37,829
2018	38,583
2019	41,350
2020	43,759
2021	45,496
Years 2022 to 2026	239,019
Post-Retirement Healthcare Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	365	$ 365
Estimated future employer contributions	400
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2017	431
2018	483
2019	511
2020	545
2021	520
Years 2022 to 2026	$ 1,724