Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Aug. 26, 2012 Hogs	May 27, 2012	May 31, 2009
Guarantor Obligations [Line Items]
Minimum quantity of hogs to be purchased under hog purchase agreement through 2013	1,200,000
Loan purchase under agreement		$ 40.8
Face value of federal income tax credits	21.2
Dispute coverage charge with insurance carrier		17.5	24.8
Favorable claim related to defense cost	11.8
Favorable claim for disputed coverage	25.0
Damages accrued in prior period	3
Litigation matter
Guarantor Obligations [Line Items]
Dispute coverage charge with insurance carrier	7.5
Compensatory damages
Guarantor Obligations [Line Items]
Favorable claim for disputed coverage	77.5
Punitive damages
Guarantor Obligations [Line Items]
Favorable claim for disputed coverage	100.0
Beatrice
Guarantor Obligations [Line Items]
Number of sites under environmental matters for which acquired company has a liability	36
Number of sites under environmental matters for which acquired company is making payments	32
Reserves for Beatrice environmental matters	69.9
Maximum period expected for disbursements on environmental matters	18 years
Leases and other commercial obligations guarantee
Guarantor Obligations [Line Items]
Maximum period of guarantee	4 Years
Guarantee obligation under purchase agreement	10.2
Potato supply agreement guarantee
Guarantor Obligations [Line Items]
Amount of supplier loans effectively guaranteed	73.2
Onion supply agreement guarantee
Guarantor Obligations [Line Items]
Guarantee obligation under purchase agreement	$ 25.0