STOCKHOLDERS' EQUITY (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Aug. 30, 2020	Aug. 25, 2019
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	$ 7,950.7	$ 7,463.7
Stock option and incentive plans	7.4	7.0
Currency translation adjustments	17.5	(11.6)
Derivative adjustments	(1.2)	(1.8)
Activities of noncontrolling interests	0.8	0.5
Pension and postretirement healthcare benefits	(0.3)	(11.4)
Dividends declared on common stock; $0.2125 per share	(103.8)	(103.4)
Net income attributable to Conagra Brands, Inc.	329.0	173.8
Balance at ending of period	8,199.0	7,516.8
Accounting Standards Update 2016-13
Schedule Of Stockholders Equity Accounts [Line Items]
Adoption of ASU	(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	$ 2,323.2	$ 2,286.0
Stock option and incentive plans	(25.4)	(8.5)
Balance at ending of period	2,297.8	2,277.5
Retained Earnings
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	5,471.2	5,047.9
Stock option and incentive plans	(0.7)	(0.3)
Dividends declared on common stock; $0.2125 per share	(103.8)	(103.4)
Net income attributable to Conagra Brands, Inc.	329.0	173.8
Balance at ending of period	5,694.6	5,118.0
Retained Earnings | Accounting Standards Update 2016-13
Schedule Of Stockholders Equity Accounts [Line Items]
Adoption of ASU	(1.1)
Accumulated Other Comprehensive Income (Loss)
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	(109.6)	(110.3)
Currency translation adjustments	15.3	(8.9)
Derivative adjustments	(1.2)	(1.8)
Pension and postretirement healthcare benefits	(0.3)	(11.4)
Balance at ending of period	(95.8)	(132.4)
Treasury Stock
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	(2,729.9)	(2,760.2)
Stock option and incentive plans	33.5	16.0
Balance at ending of period	(2,696.4)	(2,744.2)
Noncontrolling Interests
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	74.6	79.1
Stock option and incentive plans		(0.2)
Currency translation adjustments	2.2	(2.7)
Activities of noncontrolling interests	0.8	0.5
Balance at ending of period	$ 77.6	$ 76.7