Employee and Retiree Benefit Plans (Amounts Included in Accumulated Other Comprehensive Income Not Recognized in Net Periodic Benefit Expense) (Details) $ in Thousands	Dec. 31, 2016 USD ($)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ (247,622)
Prior service (cost) credit	(6,831)
Amounts included in accumulated other comprehensive loss which have not been recognized in net periodic benefit expense	(254,453)
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	(2,858)
Prior service (cost) credit	112
Amounts included in accumulated other comprehensive loss which have not been recognized in net periodic benefit expense	$ (2,746)