Employee and Retiree Benefit Plans (Amounts Included in Accumulated Other Comprehensive Income Not Recognized in Net Periodic Benefit Expense) (Details) $ in Thousands	Dec. 31, 2015 USD ($)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ (242,809)
Prior service (cost) credit	(8,903)
Amounts included in accumulated other comprehensive loss which have not been recognized in net periodic benefit expense	(251,712)
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	(13,495)
Prior service (cost) credit	207
Amounts included in accumulated other comprehensive loss which have not been recognized in net periodic benefit expense	$ (13,288)