Other Comprehensive Income (Reclassification out of AOCI) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 30, 2013		Mar. 31, 2012
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales and operating expenses	$ (322,686)		$ (276,469)
Interest expense	(5,625)		(6,925)
Amortization of prior service cost	(15)		(22)
Amortization of actuarial loss	(1,300)		(1,189)
Total before tax	52,823		44,741
Income tax benefit/(expense)	(20,418)		(16,170)
Net income	32,405		28,571
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net income	(814)		(1,321)
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	(15)		(945)
Income tax benefit/(expense)	6		366
Net income	9		(579)
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	(57)		(713)
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	42		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		(232)
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]
Amortization of actuarial loss	(1,300)	[1]	(1,189)	[1]
Total before tax	(1,315)		(1,211)
Income tax benefit/(expense)	510		469
Net income	$ 805		$ (742)

[1] These items are included in the computation of net periodic pension cost. See Note 12 Employee Benefit Plans for additional information.