EARNINGS PER SHARE - Computation of Basic and Diluted Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	May 31, 2020	Feb. 23, 2020	Nov. 24, 2019	Aug. 25, 2019	May 26, 2019	Feb. 24, 2019	Nov. 25, 2018	Aug. 26, 2018	May 31, 2020	May 26, 2019	May 27, 2018
Numerator:
Net income attributable to Lamb Weston Holdings, Inc.	$ (1.6)	$ 111.4	$ 140.4	$ 115.7	$ 110.4	$ 141.4	$ 119.0	$ 107.8	$ 365.9	$ 478.6	$ 416.8
Less: Increase in redemption value of noncontrolling interests in excess of earnings allocated, net of tax benefits										10.8	2.7
Net income available to Lamb Weston common stockholders									$ 365.9	$ 467.8	$ 414.1
Denominator:
Basic weighted average common shares outstanding									146.2	146.5	146.3
Add: Dilutive effect of employee incentive plans									0.9	0.8	0.7
Diluted weighted average common shares outstanding									147.1	147.3	147.0
Earnings per share
Basic (in dollars per share)	$ (0.01)	$ 0.76	$ 0.96	$ 0.79	$ 0.76	$ 0.96	$ 0.74	$ 0.73	$ 2.50	$ 3.19	$ 2.83
Diluted (in dollars per share)	$ (0.01)	$ 0.76	$ 0.95	$ 0.79	$ 0.75	$ 0.95	$ 0.74	$ 0.73	$ 2.49	$ 3.18	$ 2.82