STOCKHOLDERS' EQUITY (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended						9 Months Ended
	Feb. 23, 2020	Nov. 24, 2019	Aug. 25, 2019	Feb. 24, 2019	Nov. 25, 2018	Aug. 26, 2018	Feb. 23, 2020	Feb. 24, 2019
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	$ 7,690.6	$ 7,516.8	$ 7,463.7	$ 7,303.3	$ 3,815.0	$ 3,756.6	$ 7,463.7	$ 3,756.6
Stock option and incentive plans	13.3	13.5	7.0	4.0	6.0	9.8
Currency translation adjustment, net	3.8	3.5	(11.6)	7.4	(15.7)	(3.0)
Issuance of treasury shares					2,816.3
Issuance of common stock					555.7
Derivative adjustment, net	(0.9)	(1.4)	(1.8)	(2.0)	79.2	(43.4)
Activities of noncontrolling interests	0.3	1.8	0.5	0.1	2.2
Pension and postretirement healthcare benefits	56.0	(0.7)	(11.4)	(0.1)	(0.2)	(0.5)
Dividends declared on common stock; $0.2125 per share	(103.6)	(103.4)	(103.4)	(103.2)	(86.8)	(83.2)
Net income attributable to Conagra Brands, Inc.	204.4	260.5	173.8	242.0	131.6	178.2	638.7	551.8
Balance at ending of period	7,863.9	7,690.6	7,516.8	7,451.5	7,303.3	3,815.0	7,863.9	7,451.5
Accounting Standards Update 2016-01
Schedule Of Stockholders Equity Accounts [Line Items]
Adoption of ASU						0.0
Accounting Standards Update 2014-09
Schedule Of Stockholders Equity Accounts [Line Items]
Adoption of ASU						0.5
Common Stock
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	$ 2,921.2	$ 2,921.2	$ 2,921.2	$ 2,921.2	$ 2,839.7	$ 2,839.7	$ 2,921.2	$ 2,839.7
Balance at beginning of period (in shares)	584.2	584.2	584.2	584.2	567.9	567.9	584.2	567.9
Issuance of common stock					$ 81.5
Issuance of common stock (in shares)					16.3
Balance at ending of period	$ 2,921.2	$ 2,921.2	$ 2,921.2	$ 2,921.2	$ 2,921.2	$ 2,839.7	$ 2,921.2	$ 2,921.2
Balance at end of period (in shares)	584.2	584.2	584.2	584.2	584.2	567.9	584.2	584.2
Additional Paid-in Capital
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	$ 2,286.9	$ 2,277.5	$ 2,286.0	$ 2,280.8	$ 1,165.6	$ 1,180.0	$ 2,286.0	$ 1,180.0
Stock option and incentive plans	6.1	9.4	(8.5)	(3.9)	2.2	(14.1)
Issuance of treasury shares					638.2
Issuance of common stock					474.2
Activities of noncontrolling interests				0.3	0.6	(0.3)
Balance at ending of period	2,293.0	2,286.9	2,277.5	2,277.2	2,280.8	1,165.6	2,293.0	2,277.2
Retained Earnings
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	5,274.7	5,118.0	5,047.9	4,886.4	4,841.5	4,744.9	5,047.9	4,744.9
Stock option and incentive plans	(0.3)	(0.4)	(0.3)	0.1	0.1	0.5
Dividends declared on common stock; $0.2125 per share	(103.6)	(103.4)	(103.4)	(103.2)	(86.8)	(83.2)
Net income attributable to Conagra Brands, Inc.	204.4	260.5	173.8	242.0	131.6	178.2
Balance at ending of period	5,375.2	5,274.7	5,118.0	5,025.3	4,886.4	4,841.5	5,375.2	5,025.3
Retained Earnings | Accounting Standards Update 2016-01
Schedule Of Stockholders Equity Accounts [Line Items]
Adoption of ASU						0.6
Retained Earnings | Accounting Standards Update 2014-09
Schedule Of Stockholders Equity Accounts [Line Items]
Adoption of ASU						0.5
Accumulated Other Comprehensive Income (Loss)
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	(131.0)	(132.4)	(110.3)	(91.5)	(155.7)	(110.5)	(110.3)	(110.5)
Currency translation adjustment, net	3.9	3.5	(8.9)	7.9	(14.8)	(0.7)
Derivative adjustment, net	(0.9)	(1.4)	(1.8)	(2.0)	79.2	(43.4)
Pension and postretirement healthcare benefits	56.0	(0.7)	(11.4)	(0.1)	(0.2)	(0.5)
Balance at ending of period	(72.0)	(131.0)	(132.4)	(85.7)	(91.5)	(155.7)	(72.0)	(85.7)
Accumulated Other Comprehensive Income (Loss) | Accounting Standards Update 2016-01
Schedule Of Stockholders Equity Accounts [Line Items]
Adoption of ASU						(0.6)
Treasury Stock
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	(2,739.7)	(2,744.2)	(2,760.2)	(2,772.8)	(4,954.6)	(4,977.9)	(2,760.2)	(4,977.9)
Stock option and incentive plans	7.3	4.5	16.0	7.8	3.7	23.3
Issuance of treasury shares					2,178.1
Balance at ending of period	(2,732.4)	(2,739.7)	(2,744.2)	(2,765.0)	(2,772.8)	(4,954.6)	(2,732.4)	(2,765.0)
Noncontrolling Interests
Schedule Of Stockholders Equity Accounts [Line Items]
Balance at beginning of period	78.5	76.7	79.1	79.2	78.5	80.4	79.1	80.4
Stock option and incentive plans	0.2		(0.2)			0.1
Currency translation adjustment, net	(0.1)		(2.7)	(0.5)	(0.9)	(2.3)
Activities of noncontrolling interests	0.3	1.8	0.5	(0.2)	1.6	0.3
Balance at ending of period	$ 78.9	$ 78.5	$ 76.7	$ 78.5	$ 79.2	$ 78.5	$ 78.9	$ 78.5