SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Summary of Reclassifications From Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Feb. 25, 2018	Feb. 26, 2017	Feb. 25, 2018	Feb. 26, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest expense, net	$ (39.8)	$ (45.7)	$ (114.2)	$ (158.0)
Selling, general and administrative expenses	330.2	349.7	876.5	999.3
Income from continuing operations before income taxes and equity method investment earnings	228.8	225.6	785.4	655.8
Income tax expense	91.4	(67.9)	(138.1)	(315.5)
Net income attributable to Conagra Brands, Inc.	362.8	179.7	738.8	488.0
Reclassification out of accumulated other comprehensive loss | Derivative adjustments, net of reclassification adjustments
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest expense, net	0.0	(0.2)	0.1	(0.2)
Income from continuing operations before income taxes and equity method investment earnings	0.0	(0.2)	0.1	(0.2)
Income tax expense	0.0	0.1	0.0	0.1
Net income attributable to Conagra Brands, Inc.	0.0	(0.1)	0.1	(0.1)
Reclassification out of accumulated other comprehensive loss | Net prior service benefit
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Selling, general and administrative expenses	(0.1)	(0.9)	(0.4)	(2.9)
Income from continuing operations before income taxes and equity method investment earnings	(0.1)	13.0	(0.4)	11.2
Income tax expense	0.0	(5.0)	0.1	(4.3)
Net income attributable to Conagra Brands, Inc.	(0.1)	8.0	(0.3)	6.9
Reclassification out of accumulated other comprehensive loss | Pension settlement
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Selling, general and administrative expenses	0.0	13.8	0.0	13.8
Reclassification out of accumulated other comprehensive loss | Net actuarial loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Selling, general and administrative expenses	$ 0.0	$ 0.1	$ 0.0	$ 0.3