Other Comprehensive Income (Reclassification out of AOCI) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 29, 2013		Jun. 30, 2012		Jun. 29, 2013		Jun. 30, 2012
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales and operating expenses	$ (309,922)		$ (314,138)		$ (632,608)		$ (590,607)
Interest expense	(5,669)		(5,753)		(11,294)		(12,678)
Amortization of prior service cost	15		22		30		44
Amortization of actuarial loss	1,300		1,189		2,600		2,378
Total before tax	42,753		57,829		95,576		102,570
Income tax benefit/(expense)	(16,335)		(21,604)		(36,753)		(37,774)
Net income	26,418		36,225		58,823		64,796
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net income	(125)		(940)		(939)		(2,261)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	1,110		(323)		1,095		(1,268)
Income tax benefit/(expense)	(430)		125		(424)		491
Net income	680		(198)		671		(777)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Natural Gas Swap [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales and operating expenses	244		(295)		187		(1,008)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Corn Option [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales and operating expenses	866		0		908		0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Interest Rate Swap [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	0		(28)		0		(260)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Translation Adjustment [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Amortization of prior service cost	(15)	[1]	(22)	[1]	(30)	[1]	(44)	[1]
Amortization of actuarial loss	(1,300)	[1]	(1,189)	[1]	(2,600)	[1]	(2,378)	[1]
Total before tax	(1,315)		(1,211)		(2,630)		(2,422)
Income tax benefit/(expense)	510		469		1,020		938
Net income	$ (805)		$ (742)		$ (1,610)		$ (1,484)

[1] These items are included in the computation of net periodic pension cost. See Note 8 Employee Benefit Plans for additional information.