Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Paid-In Capital	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Total RPM International Inc. Equity	Total RPM International Inc. Equity Cumulative Effect, Period of Adoption, Adjustment	Noncontrolling Interests
Beginning Balance at May. 31, 2018	$ 1,633,538	$ (2,833)	$ 1,336	$ 982,067	$ (236,318)	$ (459,048)	$ 1,342,736	$ (2,833)	$ 1,630,773	$ (2,833)	$ 2,765
Beginning Balance (in shares) at May. 31, 2018			133,647,000
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201409Member
Net income	$ 267,687						266,558		266,558		1,129
Other comprehensive income (loss)	(118,514)					(118,580)			(118,580)		66
Dividends declared and paid	(181,409)						(181,409)		(181,409)
Other noncontrolling interest activity	(1,307)										(1,307)
Share repurchases under repurchase program	$ (200,222)		$ (33)	33	(200,222)				(200,222)
Share repurchases under repurchase program (in shares)	(3,286,907)		(3,287,000)
Stock compensation expense and other deferred compensation, shares granted less shares returned for taxes	$ 14,473		$ 1	35,437	(20,965)				14,473
Stock compensation expense and other deferred compensation, shares granted less shares returned for taxes (in shares)			36,000
Convertible bond redemption	(2,808)		$ 6	(23,029)	20,215				(2,808)
Convertible bond redemption (in shares)			599,000
Ending Balance at May. 31, 2019	1,408,605		$ 1,310	994,508	(437,290)	(577,628)	1,425,052		1,405,952		2,653
Ending Balance (in shares) at May. 31, 2019			130,995,000
Net income	305,082						304,385		304,385		697
Other comprehensive income (loss)	(139,888)					(139,869)			(139,869)		(19)
Dividends declared and paid	(185,101)						(185,101)		(185,101)
Other noncontrolling interest activity	(1,113)										(1,113)
Share repurchases under repurchase program	$ (125,000)		$ (20)	20	(125,000)				(125,000)
Share repurchases under repurchase program (in shares)	(2,041,847)		(2,042,000)
Stock compensation expense and other deferred compensation, shares granted less shares returned for taxes	$ 2,078		$ 5	19,900	(17,827)				2,078
Stock compensation expense and other deferred compensation, shares granted less shares returned for taxes (in shares)			558,000
Ending Balance at May. 31, 2020	1,264,663		$ 1,295	1,014,428	(580,117)	(717,497)	1,544,336		1,262,445		2,218
Ending Balance (in shares) at May. 31, 2020			129,511,000
Net income	503,500						502,643		502,643		857
Other comprehensive income (loss)	202,745					202,613			202,613		132
Dividends declared and paid	(194,720)						(194,720)		(194,720)
Other noncontrolling interest activity	(1,246)										(1,246)
Share repurchases under repurchase program	$ (49,956)		$ (6)	6	(49,956)				(49,956)
Share repurchases under repurchase program (in shares)	(594,061)		(594,000)
Stock compensation expense and other deferred compensation, shares granted less shares returned for taxes	$ 18,039		$ 6	40,966	(22,933)				18,039
Stock compensation expense and other deferred compensation, shares granted less shares returned for taxes (in shares)			656,000
Ending Balance at May. 31, 2021	$ 1,743,025		$ 1,295	$ 1,055,400	$ (653,006)	$ (514,884)	$ 1,852,259		$ 1,741,064		$ 1,961
Ending Balance (in shares) at May. 31, 2021			129,573,000