Components of Total Equity and Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Nov. 30, 2015	Nov. 30, 2014	Nov. 30, 2015	Nov. 30, 2014
Stockholders Equity Note [Line Items]
Total equity, beginning of period	$ 1,297,022	$ 1,634,368	$ 1,293,465	$ 1,578,594
Net income	84,149	73,856	184,511	178,695
Other Comprehensive Income:
Foreign currency translation adjustments	(53,814)	(91,222)	(84,420)	(112,488)
Pension and other postretirement benefit liability adjustments, net of tax	3,640	4,985	7,800	7,914
Unrealized (loss) gain on securities, net of tax	369	(2,567)	(6,715)	(2,491)
Total other comprehensive (loss)	(49,805)	(88,521)	(83,335)	(106,848)
Unrealized gain on derivatives, net of tax		283		217
Total Comprehensive Income (Loss)	34,344	(14,665)	101,176	71,847
Dividends paid	(36,642)	(34,776)	(71,276)	(66,763)
Other noncontrolling interest activity	(1,373)		(1,373)
Shares repurchased and returned for taxes	(9,944)	(1,788)	(45,292)	(1,788)
Stock option exercises, net of shares returned for taxes		4,956		505
Stock based compensation expense	8,817	(3,796)	15,524	1,904
Restricted awards, net		7,179		7,179
Total Equity, end of period	1,292,224	1,591,478	1,292,224	1,591,478
Total RPM International Inc. Equity
Stockholders Equity Note [Line Items]
Total equity, beginning of period	1,294,402	1,436,234	1,291,392	1,382,844
Net income	83,433	69,766	183,248	168,845
Other Comprehensive Income:
Foreign currency translation adjustments	(53,814)	(89,462)	(84,420)	(107,200)
Pension and other postretirement benefit liability adjustments, net of tax	3,640	4,374	7,800	7,134
Unrealized (loss) gain on securities, net of tax	369	(2,574)	(6,715)	(2,491)
Total other comprehensive (loss)	(49,805)	(87,439)	(83,335)	(102,386)
Unrealized gain on derivatives, net of tax		223		171
Total Comprehensive Income (Loss)	33,628	(17,673)	99,913	66,459
Dividends paid	(36,642)	(34,776)	(71,276)	(66,763)
Other noncontrolling interest activity		51		47
Shares repurchased and returned for taxes	(9,944)	(1,788)	(45,292)	(1,788)
Stock option exercises, net of shares returned for taxes		4,956		505
Stock based compensation expense	8,817	(3,796)	15,524	1,904
Restricted awards, net		7,179		7,179
Total Equity, end of period	1,290,261	1,390,387	1,290,261	1,390,387
Noncontrolling Interest
Stockholders Equity Note [Line Items]
Total equity, beginning of period	2,620	198,134	2,073	195,750
Net income	716	4,090	1,263	9,850
Other Comprehensive Income:
Foreign currency translation adjustments		(1,760)		(5,288)
Pension and other postretirement benefit liability adjustments, net of tax		611		780
Unrealized (loss) gain on securities, net of tax		7
Total other comprehensive (loss)		(1,082)		(4,462)
Unrealized gain on derivatives, net of tax		60		46
Total Comprehensive Income (Loss)	716	3,008	1,263	5,388
Other noncontrolling interest activity	(1,373)	(51)	(1,373)	(47)
Total Equity, end of period	$ 1,963	$ 201,091	$ 1,963	$ 201,091