Acquisitions and Dispositions (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended									12 Months Ended			0 Months Ended	3 Months Ended	12 Months Ended			0 Months Ended	1 Months Ended	0 Months Ended	12 Months Ended	0 Months Ended		12 Months Ended							12 Months Ended					0 Months Ended					0 Months Ended
	Dec. 31, 2011	Oct. 01, 2011	Jul. 02, 2011	Apr. 02, 2011	Jan. 01, 2011		Oct. 02, 2010	Jul. 03, 2010	Apr. 03, 2010	Dec. 31, 2011	Jan. 01, 2011	Jan. 02, 2010	Dec. 17, 2010 Griffin Transaction [Member]	Jan. 01, 2011 Griffin Transaction [Member]	Dec. 31, 2011 Griffin Transaction [Member]	Jan. 01, 2011 Griffin Transaction [Member]	Jan. 02, 2010 Griffin Transaction [Member]	May 28, 2010 Nebraska Transaction [Member]	Dec. 31, 2009 Sanimax Transaction [Member]	Feb. 23, 2009 Boca Transaction [Member]	Dec. 31, 2011 API Transaction [Member]	Dec. 17, 2010 Common Stock [Member] Griffin Transaction [Member]	May 28, 2010 Long Term Receivable [Member] Nebraska Transaction [Member]	Dec. 31, 2011 Long Term Receivable [Member] API Transaction [Member]	Dec. 31, 2011 Goodwill [Member] API Transaction [Member]	Dec. 31, 2011 Bakery [Member]	Jan. 01, 2011 Bakery [Member]	Jan. 02, 2010 Bakery [Member]	Dec. 31, 2011 Bakery [Member] Griffin Transaction [Member]	Dec. 17, 2010 Bakery [Member] Griffin Transaction [Member]	Dec. 31, 2011 Rendering [Member]	Jan. 01, 2011 Rendering [Member]	Jan. 02, 2010 Rendering [Member]	Dec. 31, 2011 Rendering [Member] Griffin Transaction [Member]	Dec. 17, 2010 Rendering [Member] Griffin Transaction [Member]	Dec. 17, 2010 Trade Names [Member] Griffin Transaction [Member] year	Dec. 17, 2010 Permits [Member] Griffin Transaction [Member] year	Dec. 17, 2010 Routes [Member] Griffin Transaction [Member] year	Dec. 17, 2010 Noncompete And Leasehold Agreements [Member] Griffin Transaction [Member] year	Dec. 17, 2010 Trade Names [Member] Griffin Transaction [Member]	Sep. 11, 2009 Little Rock,AR Grease Trap Plant [Member]
Business Acquisition [Line Items]
Revenues																$ 27,700,000
Net income	29,497,000	41,132,000	52,227,000	46,562,000	10,012,000	[1]	11,382,000	11,371,000	11,478,000	169,418,000	44,243,000	41,790,000				1,900,000										62,259,000	1,425,000	0			329,791,000	132,502,000	109,697,000
Business Acquisition, Griffin, Pro Forma Information [Abstract]
Net sales																1,339,589,000	1,123,108,000
Income from continuing operations																133,184,000	91,299,000
Net income																85,344,000	57,062,000
Earnings Per Share
Basic (in dollars per share)																$ 0.92	$ 0.62
Diluted (in dollars per share)																$ 0.91	$ 0.61
Total consideration paid													872,197,000						19,000,000	12,500,000
Cash consideration paid													740,500,000					15,300,000
Issuance of Darling common stock																						10.0
Fair market value per share at closing																						$ 13.06
Fair market value at closing																						130,600,000
Escrow receivable for certain over funding of working capital													16,300,000
Accrued expense for the Company's election to step up the tax basis													13,600,000
Long-term liability of contingent consideration for the true-up adjustment													3,800,000		0
Working capital adjustment, goodwill															300,000														1,700,000					2,000,000
Cash received from escrow															16,400,000
Cash Paid For Step Up in Tax Basis															13,800,000
Tax step up basis original accrual change															200,000
Step Up Tax Basis Benefit Period													15 years
True up adjustment additional cash maximum															15,000,000
Per share amount true up market price less than															$ 10.002
Per share amount true up market price exceeds															$ 10.002
If the true-up market price exceeds $10.002 per share															No additional consideration will be paid
Business Acquisition, Cost of Acquired Entity, Transaction Costs													37,700,000
Acquisition costs										0	10,798,000	468,000	10,600,000	13,700,000
Interest Expense										37,163,000	8,737,000	3,105,000	3,100,000
Deferred Finance Costs, Gross													24,000,000
Business Acquisition, Purchase Price Allocation [Abstract]
Cash													350,000
Accounts receivable													33,872,000
Inventory													22,623,000
Other current assets													2,558,000
Other assets													3,103,000
Other																				100,000			100,000
Deferred tax asset													2,538,000
Identifiable intangibles													349,775,000						4,800,000	3,300,000
Property and equipment													234,115,000					9,600,000	4,700,000	3,300,000
Goodwill													294,669,000					2,800,000	9,900,000	5,800,000										53,150,000					241,519,000
Accounts payable													(46,275,000)
Accrued expenses													(14,127,000)						400,000
Other liabilities													(11,004,000)
Purchase price													872,197,000						19,000,000	12,500,000
Business Acquisition, Purchase Price Allocation, Goodwill, Expected Tax Deductible Amount													294,700,000
Business Acquisition, Purchase Price Allocation, Intangible Assets Not Amortizable																																								92,000,000
Finite-lived Intangible Assets																		2,800,000																		500,000	228,400,000	25,100,000	3,800,000
Acquired finite-lived Intangible assets, weighted-average useful life																		11	8	9																15	13	5	5
Payments for (Proceeds from) Previous Acquisition																					1,300,000
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Asset																								300,000	1,600,000
Disposal of Discontinued Operation for Cash and Other Consideration																																									$ 1,600,000

[1] Included in net income in the fourth quarter of fiscal 2010 are costs incurred as part of the Griffin Transaction for consulting, legal and financing in the amount of approximately $13.7 million.