Business Segments (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 29, 2012 segment	Sep. 29, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Oct. 01, 2011	Jul. 02, 2011	Apr. 02, 2011	Dec. 29, 2012 segment		Dec. 31, 2011		Jan. 01, 2011		Dec. 31, 2011 Griffin and Nebraska Transactions [Member]	Jan. 02, 2010 Sanimax Transaction and Boca Transaction [Member]	Dec. 29, 2012 Geographic Concentration Risk [Member] country	Dec. 31, 2011 Geographic Concentration Risk [Member] country	Jan. 01, 2011 Geographic Concentration Risk [Member] country	Dec. 29, 2012 Geographic Concentration Risk [Member] Maximum [Member]	Dec. 29, 2012 Rendering [Member]	Dec. 31, 2011 Rendering [Member]	Jan. 01, 2011 Rendering [Member]	Dec. 29, 2012 Rendering [Member] Fat [Member]	Dec. 31, 2011 Rendering [Member] Fat [Member]	Jan. 01, 2011 Rendering [Member] Fat [Member]	Dec. 29, 2012 Rendering [Member] Protein [Member]	Dec. 31, 2011 Rendering [Member] Protein [Member]	Jan. 01, 2011 Rendering [Member] Protein [Member]
Segment Reporting Information [Line Items]
Number Of Foreign Countries Comprising More Than 5 Percent Of Entity's Consolidated Revenue																	0	0	0
Concentration Risk, Percentage																				5.00%
Number of Business Segments	2								2
Net sales	$ 424,915	$ 452,732	$ 436,674	$ 387,108	$ 430,866	$ 455,875	$ 470,610	$ 439,898	$ 1,701,429		$ 1,797,249		$ 724,909								$ 1,406,061	$ 1,501,280	$ 714,685	$ 809,700	$ 950,800	$ 399,100	$ 496,200	$ 447,700	$ 243,500
Capital expenditures									$ 115,413	[1]	$ 60,153	[1]	$ 24,720	[1]	$ 600	$ 243,700					$ 70,873	$ 51,888	$ 21,431

[1] Excludes the capital assets acquired as part of the acquisition of assets related to the BioPur acquisition in fiscal 2012 of approximately $0.6 million and the Griffin Transaction and Nebraska Transaction in fiscal 2010 of approximately $243.7 million