DISCONTINUED OPERATIONS AND OTHER DIVESTITURES - Summary of Comparative Financial Results (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	May 26, 2019	Feb. 24, 2019	Nov. 25, 2018	Aug. 26, 2018	May 27, 2018	Feb. 25, 2018	Nov. 26, 2017	Aug. 27, 2017	May 26, 2019	May 27, 2018	May 28, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (loss) from discontinued operations, net of tax	$ 0.0	$ 0.0	$ (1.9)	$ 0.0	$ (0.3)	$ 14.5	$ 0.4	$ (0.3)	$ (1.9)	$ 14.3	$ 102.0
Net income (loss) from discontinued operations attributable to Conagra Brands, Inc.									(1.9)	14.3	95.2
Lamb Weston | Spinoff
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net sales									0.0	0.0	1,407.9
Income (loss) from operations of discontinued operations before income taxes									0.0	(0.3)	172.3
Income (loss) before income taxes and equity method investment earnings									0.0	(0.3)	172.3
Income tax expense (benefit)									2.8	(14.6)	87.5
Equity method investment earnings									0.0	0.0	15.9
Income (loss) from discontinued operations, net of tax									(2.8)	14.3	100.7
Less: Net income attributable to noncontrolling interests									0.0	0.0	6.8
Net income (loss) from discontinued operations attributable to Conagra Brands, Inc.									(2.8)	14.3	93.9
Private Brands | Discontinued operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on sale of business									0.0	0.0	(1.6)
Income (loss) from operations of discontinued operations before income taxes									0.9	0.4	3.9
Income (loss) before income taxes and equity method investment earnings									0.9	0.4	2.3
Income tax expense (benefit)									0.0	0.5	(0.3)
Income (loss) from discontinued operations, net of tax									$ 0.9	$ (0.1)	$ 2.6