Employee and Retiree Benefit Plans (Components of Net Periodic Benefit Expense) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 22,470	$ 26,346	$ 23,500
Interest cost	33,680	30,903	29,869
Expected return on plan assets	(33,723)	(28,974)	(25,826)
Amortization of prior service cost	899	1,006	1,254
Amortization of transitional liability (asset)	(480)	(514)	(529)
Recognized actuarial loss	9,471	17,338	16,389
Defined Benefit Plan, Gross Periodic Benefit Cost, Total	32,317	46,105	44,657
Termination benefits expense		849	6,177
Curtailment expense (benefit)		1,365
Net periodic benefit expense	32,317	48,319	50,834
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2,459	4,566	3,958
Interest cost	4,617	5,189	5,174
Amortization of prior service cost	(82)	(143)	(173)
Amortization of transitional liability (asset)		8	8
Recognized actuarial loss	5	1,484	1,317
Defined Benefit Plan, Gross Periodic Benefit Cost, Total	6,999	11,104	10,284
Curtailment expense (benefit)		(442)
Net periodic benefit expense	$ 6,999	$ 10,662	$ 10,284