STOCKHOLDERS' EQUITY - Reconciliation of Stockholders' Equity Accounts (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Aug. 29, 2021	Aug. 30, 2020
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	$ 8,631.4	$ 7,950.7
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201613Member
Stock option and incentive plans	(14.8)	$ 7.4
Currency translation adjustments	(15.7)	17.5
Repurchase of common shares	(50.0)
Derivative adjustments	(2.1)	(1.2)
Activities of noncontrolling interests	0.3	0.8
Pension and postretirement healthcare benefits	1.3	(0.3)
Dividends declared on common stock	(149.9)	(103.8)
Net income attributable to Conagra Brands, Inc.	235.4	329.0
Balance at ending of period	8,635.9	8,199.0
Cumulative Effect, Period of Adoption, Adjustment
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period		(1.1)
Common Stock
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	$ 2,921.2	$ 2,921.2
Balance at beginning of period (in shares)	584.2	584.2
Balance at ending of period	$ 2,921.2	$ 2,921.2
Balance at end of period (in shares)	584.2	584.2
Additional Paid-in Capital
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	$ 2,342.1	$ 2,323.2
Stock option and incentive plans	(37.1)	(25.4)
Balance at ending of period	2,305.0	2,297.8
Retained Earnings
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	6,262.6	5,471.2
Stock option and incentive plans	0.2	(0.7)
Dividends declared on common stock	(149.9)	(103.8)
Net income attributable to Conagra Brands, Inc.	235.4	329.0
Balance at ending of period	6,348.3	5,694.6
Retained Earnings | Cumulative Effect, Period of Adoption, Adjustment
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period		(1.1)
Accumulated Other Comprehensive Income (Loss)
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	5.8	(109.6)
Currency translation adjustments	(14.4)	15.3
Derivative adjustments	(2.1)	(1.2)
Pension and postretirement healthcare benefits	1.3	(0.3)
Balance at ending of period	(9.4)	(95.8)
Treasury Stock
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	(2,979.9)	(2,729.9)
Stock option and incentive plans	21.8	33.5
Repurchase of common shares	(50.0)
Balance at ending of period	(3,008.1)	(2,696.4)
Noncontrolling Interests
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	79.6	74.6
Stock option and incentive plans	0.3
Currency translation adjustments	(1.3)	2.2
Activities of noncontrolling interests	0.3	0.8
Balance at ending of period	$ 78.9	$ 77.6