Components of Total Equity and Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Nov. 30, 2016	Nov. 30, 2015	Nov. 30, 2016	Nov. 30, 2015
Stockholders Equity Note [Line Items]
Total equity, beginning of period	$ 1,437,564	$ 1,297,022	$ 1,374,748	$ 1,293,465
Net (Loss) Income	(70,256)	84,149	43,138	184,511
Other Comprehensive Income:
Foreign currency translation adjustments	(51,984)	(53,814)	(63,495)	(84,420)
Pension and other postretirement benefit liability adjustments, net of tax	3,590	3,640	9,294	7,800
Unrealized (loss) gain on securities, net of tax	(895)	369	709	(6,715)
Total Other Comprehensive (Loss), net of tax	(49,289)	(49,805)	(53,492)	(83,335)
Comprehensive Income (Loss)	(119,545)	34,344	(10,354)	101,176
Dividends paid	(40,075)	(36,642)	(76,604)	(71,276)
Other noncontrolling interest activity	(894)	(1,373)	(1,806)	(1,373)
Shares repurchased and returned for taxes	(2,558)	(9,944)	(19,663)	(45,292)
Stock based compensation expense	8,842	8,817	17,013	15,524
Total Equity, end of period	1,283,334	1,292,224	1,283,334	1,292,224
Total RPM International Inc. Equity
Stockholders Equity Note [Line Items]
Total equity, beginning of period	1,435,438	1,294,402	1,372,335	1,291,392
Net (Loss) Income	(70,926)	83,433	41,843	183,248
Other Comprehensive Income:
Foreign currency translation adjustments	(51,984)	(53,814)	(63,495)	(84,420)
Pension and other postretirement benefit liability adjustments, net of tax	3,590	3,640	9,294	7,800
Unrealized (loss) gain on securities, net of tax	(895)	369	709	(6,715)
Total Other Comprehensive (Loss), net of tax	(49,289)	(49,805)	(53,492)	(83,335)
Comprehensive Income (Loss)	(120,215)	33,628	(11,649)	99,913
Dividends paid	(40,075)	(36,642)	(76,604)	(71,276)
Shares repurchased and returned for taxes	(2,558)	(9,944)	(19,663)	(45,292)
Stock based compensation expense	8,842	8,817	17,013	15,524
Total Equity, end of period	1,281,432	1,290,261	1,281,432	1,290,261
Noncontrolling Interest
Stockholders Equity Note [Line Items]
Total equity, beginning of period	2,126	2,620	2,413	2,073
Net (Loss) Income	670	716	1,295	1,263
Other Comprehensive Income:
Comprehensive Income (Loss)	670	716	1,295	1,263
Other noncontrolling interest activity	(894)	(1,373)	(1,806)	(1,373)
Total Equity, end of period	$ 1,902	$ 1,963	$ 1,902	$ 1,963