Business Segments (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 30, 2013 segment	Mar. 31, 2012
Segment Reporting Information [Line Items]
Number of Business Segments	2
Net sales	$ 445,422	$ 387,108
Rendering [Member]
Segment Reporting Information [Line Items]
Net sales	367,174	322,312
Fat [Member] \| Rendering [Member]
Segment Reporting Information [Line Items]
Net sales	199,200	194,000
Protein [Member] \| Rendering [Member]
Segment Reporting Information [Line Items]
Net sales	$ 138,900	$ 103,500

Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

Name:	us-gaap_SalesRevenueNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration