Stockholders' Equity - Reconciliation of Stockholders Equity (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended				6 Months Ended
	Nov. 25, 2012	Nov. 27, 2011	Nov. 25, 2012	Nov. 27, 2011	Nov. 25, 2012 Common Stock [Member]	May 27, 2012 Common Stock [Member]	Nov. 25, 2012 Additional Paid-in Capital [Member]	Nov. 25, 2012 Retained Earnings [Member]	Nov. 25, 2012 Accumulated Other Comprehensive Income (Loss) [Member]	Nov. 25, 2012 Treasury Stock [Member]	Nov. 25, 2012 Noncontrolling Interests [Member]
Schedule Of Stockholders Equity [Line Items]
Opening Balance			$ 4,536.0		$ 2,839.7	$ 2,839.7	$ 901.5	$ 4,765.1	$ (299.1)	$ (3,767.7)	$ 96.5
Opening Balance, Shares					567.9	567.9
Stock option and incentive plans			127.8				9.5	(0.6)		118.9
Currency translation adjustment			18.6						18.7		(0.1)
Repurchase of common shares			(244.0)							(244.0)
Derivative adjustment, net of reclassification adjustment	(0.3)	(48.3)	(3.0)	(80.2)					(3.0)
Activities of noncontrolling interests			0.8				(0.8)				1.6
Pension and postretirement healthcare benefits	0.2	18.9	1.1	19.0					1.1
Dividends declared on common stock; $0.49 per share			(198.7)					(198.7)
Net income attributable to ConAgra Foods, Inc.	211.6	180.2	461.7	274.0				461.7
Ending Balance	$ 4,700.3		$ 4,700.3		$ 2,839.7	$ 2,839.7	$ 910.2	$ 5,027.5	$ (282.3)	$ (3,892.8)	$ 98.0
Ending Balance, Shares					567.9	567.9