Employee and Retiree Benefit Plans (Components of Net Periodic Benefit Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 17,948	$ 22,470	$ 26,346
Interest cost	33,168	33,680	30,903
Expected return on plan assets	(34,016)	(33,723)	(28,974)
Amortization of prior service cost (credit)	1,560	899	1,006
Amortization of transitional (asset) liability	(1)	(480)	(514)
Recognized actuarial loss	15,147	9,471	17,338
Gross periodic benefit expense	33,806	32,317	46,105
Termination benefits expense	8,606		849
Curtailment expense (benefit)	306		1,365
Net periodic benefit expense	42,718	32,317	48,319
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	3,180	2,459	4,566
Interest cost	4,883	4,617	5,189
Amortization of prior service cost (credit)	(82)	(82)	(143)
Amortization of transitional (asset) liability			8
Recognized actuarial loss	992	5	1,484
Gross periodic benefit expense	8,973	6,999	11,104
Curtailment expense (benefit)			(442)
Net periodic benefit expense	$ 8,973	$ 6,999	$ 10,662