Components of Total Equity and Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Feb. 28, 2015	Feb. 28, 2014	Feb. 28, 2015	Feb. 28, 2014
Stockholders Equity Note [Line Items]
Total equity, beginning of period	$ 1,591,478	$ 1,493,860	$ 1,578,594	$ 1,354,933
Net income (loss)	(78,952)	16,911	99,743	192,214
Other Comprehensive Income:
Foreign currency translation adjustments	(79,275)	(12,146)	(191,763)	(1,355)
Pension and other postretirement benefit liability adjustments, net of tax	6,511	3,826	14,425	8,961
Unrealized (loss) gain on securities, net of tax	(3,488)	(2,314)	(5,979)	2,648
Unrealized gain (loss) on derivatives, net of tax	420	(484)	637	(1,369)
Total Other Comprehensive (Loss) Income, net of tax	(75,832)	(11,118)	(182,680)	8,885
Comprehensive Income	(154,784)	5,793	(82,937)	201,099
Dividends paid	(34,778)	(31,967)	(101,541)	(93,763)
Increase in equity ownership of SPHC	(147,901)		(147,901)
Shares repurchased	(25,800)	(28)	(27,588)	(6,895)
Stock option exercises, net	(984)	(1,640)	(479)	1,022
Stock based compensation expense	941	682	2,845	2,164
Restricted awards, net	5,621	5,237	12,800	13,377
Convertible bond, equity component, net of tax		13,470		13,470
Deferred financing costs, convertible bond		(492)		(492)
Total Equity, end of period	1,233,793	1,484,915	1,233,793	1,484,915
Total RPM International Inc. Equity
Stockholders Equity Note [Line Items]
Total equity, beginning of period	1,390,387	1,322,222	1,382,844	1,200,858
Net income (loss)	(57,348)	16,221	111,497	182,881
Other Comprehensive Income:
Foreign currency translation adjustments	(79,063)	(18,446)	(186,263)	(16,108)
Pension and other postretirement benefit liability adjustments, net of tax	6,346	3,469	13,480	8,430
Unrealized (loss) gain on securities, net of tax	(3,488)	(2,312)	(5,979)	2,597
Unrealized gain (loss) on derivatives, net of tax	497	(380)	668	(1,076)
Total Other Comprehensive (Loss) Income, net of tax	(75,708)	(17,669)	(178,094)	(6,157)
Comprehensive Income	(133,056)	(1,448)	(66,597)	176,724
Dividends paid	(34,778)	(31,967)	(101,541)	(93,763)
Other noncontrolling interest activity	(47)	(832)		(1,261)
Increase in equity ownership of SPHC	29,366		29,366
Shares repurchased	(25,800)	(28)	(27,588)	(6,895)
Stock option exercises, net	(984)	(1,640)	(479)	1,022
Stock based compensation expense	941	682	2,845	2,164
Restricted awards, net	5,621	5,237	12,800	13,377
Convertible bond, equity component, net of tax		13,470		13,470
Deferred financing costs, convertible bond		(492)		(492)
Total Equity, end of period	1,231,650	1,305,204	1,231,650	1,305,204
Noncontrolling Interest
Stockholders Equity Note [Line Items]
Total equity, beginning of period	201,091	171,638	195,750	154,075
Net income (loss)	(21,604)	690	(11,754)	9,333
Other Comprehensive Income:
Foreign currency translation adjustments	(212)	6,300	(5,500)	14,753
Pension and other postretirement benefit liability adjustments, net of tax	165	357	945	531
Unrealized (loss) gain on securities, net of tax		(2)		51
Unrealized gain (loss) on derivatives, net of tax	(77)	(104)	(31)	(293)
Total Other Comprehensive (Loss) Income, net of tax	(124)	6,551	(4,586)	15,042
Comprehensive Income	(21,728)	7,241	(16,340)	24,375
Other noncontrolling interest activity	47	832		1,261
Increase in equity ownership of SPHC	(177,267)		(177,267)
Total Equity, end of period	$ 2,143	$ 179,711	$ 2,143	$ 179,711