Employee and Retiree Benefit Plans (Components of Net Periodic Benefit Expense) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 6,208	$ 7,252	$ 19,048	$ 21,949
Interest cost	8,239	8,450	24,707	22,581
Expected return on plan assets	(8,506)	(8,257)	(25,514)	(21,526)
Amortization of prior service cost	227	262	680	841
Amortization of transitional liability (asset)	208	125	628	366
Recognized actuarial loss	1,735	4,591	5,201	12,882
Special termination benefits		849		849
Curtailments		1,366		1,366
Net periodic benefit expense	8,111	14,638	24,750	39,308
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	672	1,232	2,016	3,629
Interest cost	1,278	1,352	3,833	3,865
Amortization of prior service cost	(20)	(35)	(61)	(121)
Amortization of transitional liability (asset)	1	2	4	6
Recognized actuarial loss	59	391	177	1,321
Curtailments		(443)		(443)
Net periodic benefit expense	$ 1,990	$ 2,499	$ 5,969	$ 8,257