Pension and Other Post-Retirement Benefit Plans (Cash Flows) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 22,220	$ 4,476
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	0	106,742
Estimated future employer contributions	8,100
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2017	35,680
2018	36,175
2019	38,835
2020	41,192
2021	43,347
Years 2022 to 2026	232,465
Post-Retirement Healthcare Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	365	412
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	0	$ 0
Estimated future employer contributions	500
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2017	451
2018	492
2019	530
2020	529
2021	550
Years 2022 to 2026	$ 2,009