Components of Total Equity and Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Feb. 28, 2017	Feb. 29, 2016	Feb. 28, 2017	Feb. 29, 2016
Stockholders Equity Note [Line Items]
Total equity, beginning of period	$ 1,283,334	$ 1,292,224	$ 1,374,748	$ 1,293,465
Net income	12,684	19,293	55,822	203,804
Other Comprehensive Income:
Foreign currency translation adjustments	16,576	(16,214)	(46,919)	(100,634)
Pension and other postretirement benefit liability adjustments, net of tax	3,222	3,264	12,516	11,064
Unrealized gain (loss) on securities, net of tax	2,577	(7,334)	3,286	(14,049)
Total other comprehensive income (loss)	22,375	(20,284)	(31,117)	(103,619)
Total Comprehensive Income (Loss)	35,059	(991)	24,705	100,185
Dividends paid	(40,076)	(36,530)	(116,680)	(107,806)
Other noncontrolling interest activity	(153)	(186)	(1,959)	(1,559)
Shares repurchased and returned for taxes	(429)	(21,473)	(20,092)	(66,765)
Stock based compensation expense	7,992	7,476	25,005	23,000
Total Equity, end of period	1,285,727	1,240,520	1,285,727	1,240,520
Total RPM International Inc. Equity
Stockholders Equity Note [Line Items]
Total equity, beginning of period	1,281,432	1,290,261	1,372,335	1,291,392
Net income	11,928	18,582	53,771	201,830
Other Comprehensive Income:
Foreign currency translation adjustments	16,576	(16,214)	(46,919)	(100,634)
Pension and other postretirement benefit liability adjustments, net of tax	3,222	3,264	12,516	11,064
Unrealized gain (loss) on securities, net of tax	2,577	(7,334)	3,286	(14,049)
Total other comprehensive income (loss)	22,375	(20,284)	(31,117)	(103,619)
Total Comprehensive Income (Loss)	34,303	(1,702)	22,654	98,211
Dividends paid	(40,076)	(36,530)	(116,680)	(107,806)
Shares repurchased and returned for taxes	(429)	(21,473)	(20,092)	(66,765)
Stock based compensation expense	7,992	7,476	25,005	23,000
Total Equity, end of period	1,283,222	1,238,032	1,283,222	1,238,032
Noncontrolling Interest
Stockholders Equity Note [Line Items]
Total equity, beginning of period	1,902	1,963	2,413	2,073
Net income	756	711	2,051	1,974
Other Comprehensive Income:
Total Comprehensive Income (Loss)	756	711	2,051	1,974
Other noncontrolling interest activity	(153)	(186)	(1,959)	(1,559)
Total Equity, end of period	$ 2,505	$ 2,488	$ 2,505	$ 2,488