Quarterly Result of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	May 31, 2020		Feb. 29, 2020		Nov. 30, 2019		Aug. 31, 2019		May 31, 2019		Feb. 28, 2019		Nov. 30, 2018		Aug. 31, 2018		May 31, 2020		May 31, 2019		May 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Net Sales	$ 1,458,962		$ 1,173,976		$ 1,401,292		$ 1,472,764		$ 1,601,401		$ 1,140,630		$ 1,362,531		$ 1,459,989		$ 5,506,994	[1]	$ 5,564,551	[1]	$ 5,321,643	[1]
Gross Profit	553,956		434,747		529,398		574,754		635,814		409,422		493,731		549,353		2,092,855		2,088,320		2,016,548
Net Income Attributable to RPM International Inc. Stockholders	$ 109,314	[2]	$ 11,853	[2]	$ 77,030	[2]	$ 106,188	[2]	$ 133,380	[3]	$ 14,190	[3]	$ 49,224	[3]	$ 69,764	[3]	$ 304,385		$ 266,558		$ 337,770
Basic Earnings Per Share	$ 0.85		$ 0.09		$ 0.60		$ 0.82		$ 1.03		$ 0.11		$ 0.37		$ 0.52		$ 2.35		$ 2.03		$ 2.55
Diluted Earnings Per Share	0.84		0.09		0.59		0.82		1.02		0.11		0.37		0.52		$ 2.34		$ 2.01		$ 2.50
Dividends Per Share	$ 0.360		$ 0.360		$ 0.360		$ 0.350		$ 0.350		$ 0.350		$ 0.350		$ 0.320

[1] It is not practicable to obtain the information needed to disclose revenues attributable to each of our product lines.

[2] Reflects inventory-related charges of $28.8 million in our Consumer reportable segment resulting from SKU rationalization, excess and obsolescence, and exiting unprofitable product lines and regions and $3.2 million in our PCG segment resulting from the exit of unprofitable product lines and regions.  Also reflects restructuring charges totaling $33.1 million that were incurred throughout fiscal 2020, as further described in Note B, “Restructuring”.

[3] Reflects inventory-related charges of $10.5 million in our Consumer reportable segment resulting from more proactive management of inventory and $9.0 million and $1.0 million in inventory reductions related to restructuring activities in our PCG and CPG reportable segments, respectively.  Also reflects restructuring charges totaling $42.3 million that were incurred throughout fiscal 2019, as further described in Note B, “Restructuring”.