Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Feb. 28, 2018	Feb. 28, 2017	Feb. 28, 2018	Feb. 28, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net Income	$ 40,588	$ 12,684	$ 253,349	$ 55,822
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	31,133	16,576	67,453	(46,919)
Pension and other postretirement benefit liability adjustments (net of tax of $1,319; $1,863; $3,576; $6,626, respectively)	2,279	3,222	5,974	12,516
Unrealized (loss) gain on securities (net of tax of $(1,070); $1,192; $43; $1,968, respectively)	(2,380)	2,577	91	3,286
Unrealized (loss) on derivatives	(2,137)		(5,277)
Total other comprehensive income (loss)	28,895	22,375	68,241	(31,117)
Total Comprehensive Income	69,483	35,059	321,590	24,705
Less: Comprehensive Income Attributable to Noncontrolling Interests	393	756	1,234	2,051
Comprehensive Income Attributable to RPM International Inc. Stockholders	$ 69,090	$ 34,303	$ 320,356	$ 22,654