Employee and Retiree Benefit Plans (Amounts Included in Accumulated Other Comprehensive Income Not Recognized in Net Periodic Benefit Expense) (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ (239,030)
Prior service (cost) credit	(5,568)
Amounts included in accumulated other comprehensive loss which have not been recognized in net periodic benefit expense	(244,598)
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	13,969
Amounts included in accumulated other comprehensive loss which have not been recognized in net periodic benefit expense	$ 13,969