Weighted-Average Actual Target Allocation of Plan Assets (Detail) - Pension Benefits - USD ($) $ in Thousands		May 31, 2021	May 31, 2020	May 31, 2019
U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Target Allocation		100.00%
Actual Asset Allocation		$ 672,377	$ 516,550	$ 496,865
Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Target Allocation		100.00%
Actual Asset Allocation		$ 239,853	194,874	$ 187,112
Equity securities | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Target Allocation		55.00%
Actual Asset Allocation		$ 387,100	261,000
Equity securities | Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Target Allocation		37.00%
Actual Asset Allocation		$ 103,400	79,300
Fixed income securities | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Target Allocation		25.00%
Actual Asset Allocation		$ 112,000	106,400
Fixed income securities | Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Target Allocation		47.00%
Actual Asset Allocation		$ 108,200	88,200
Multi-class | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Target Allocation		20.00%
Actual Asset Allocation		$ 150,800	118,200
Cash | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Actual Asset Allocation	[1]	22,300	30,800
Cash | Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Actual Asset Allocation		100	100
Real Estate | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Actual Asset Allocation		$ 200	200
Real Estate | Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Target Allocation		16.00%
Actual Asset Allocation		$ 28,200	$ 27,300

[1] The larger than target cash position at May 31, 2021 results from our February 2021 contribution to the RPM International Inc. Retirement Plan because of our plans to invest the February contribution over a period of time, due to dollar cost averaging.