Schedule of Reconciliation of Income and Average Share Amounts to Compute Basic and Diluted Earnings Per Share (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Aug. 26, 2012	Aug. 28, 2011
Net Income available to ConAgra Foods, Inc. common stockholders:
Income from continuing operations attributable to ConAgra Foods, Inc. common stockholders	$ 250.1	$ 93.7
Income from discontinued operations, net of tax, attributable to ConAgra Foods, Inc. common stockholders		0.1
Net income attributable to ConAgra Foods, Inc.	250.1	93.8
Less: Increase in redemption value of noncontrolling interests in excess of earnings allocated	(0.4)	(0.3)
Net income available to ConAgra Foods, Inc. common stockholders	$ 249.7	$ 93.5
Weighted average shares outstanding
Basic weighted average shares outstanding	407.1	412.7
Add: Dilutive effect of stock options, restricted stock awards, and other dilutive securities	4.9	5.4
Diluted weighted average shares outstanding	412.0	418.1