QUARTERLY FINANCIAL DATA (unaudited) - Financial Information (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended								12 Months Ended
	Jul. 20, 2017	May 28, 2017	Feb. 26, 2017	Nov. 27, 2016	Aug. 28, 2016	May 29, 2016	Feb. 28, 2016	Nov. 29, 2015	Aug. 30, 2015	May 28, 2017	May 29, 2016	May 31, 2015
QUARTERLY FINANCIAL DATA (unaudited)
Net sales		$ 832.5	$ 768.5	$ 790.7	$ 776.3	$ 777.0	$ 728.7	$ 740.3	$ 747.8	$ 3,168.0	$ 2,993.8	$ 2,925.0
Gross profit		200.0	207.0	198.9	180.6	182.4	181.9	161.8	141.3	786.5	667.4	587.3
Income before income taxes and equity method earnings		95.9	118.9	118.7	123.5	50.3	125.8	108.0	83.3	457.1	367.4	375.3
Income tax expense		41.2	44.0	33.9	51.0	20.3	53.2	38.7	32.3	170.2	144.5	140.4
Net income attributable to Lamb Weston Holdings, Inc.		$ 75.9	$ 84.2	$ 87.2	$ 79.6	$ 42.6	$ 107.4	$ 73.3	$ 62.0	$ 326.9	$ 285.3	$ 268.3
Earnings per share
Basic (in dollars per share)		$ 0.52	$ 0.57	$ 0.59	$ 0.54	$ 0.29	$ 0.71	$ 0.50	$ 0.42	$ 2.22	$ 1.92	$ 1.83
Diluted (in dollars per share)		0.51	0.57	$ 0.59	$ 0.54	$ 0.29	$ 0.71	$ 0.50	$ 0.42	2.22	$ 1.92	$ 1.83
Dividends declared per common share (in dollars per share)	$ 0.1875	$ 0.1875	$ 0.1875							$ 0.375