Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Nov. 30, 2017	Nov. 30, 2016	Nov. 30, 2017	Nov. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net Income (Loss)	$ 95,858	$ (70,256)	$ 212,761	$ 43,138
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(8,158)	(51,984)	36,320	(63,495)
Pension and other postretirement benefit liability adjustments (net of tax of $1,611; $1,963; $2,257; $4,762, respectively)	3,066	3,590	3,695	9,294
Unrealized (loss) gain on securities (net of tax of $1,176; $(320); $1,027; $776, respectively)	2,549	(895)	2,471	709
Unrealized (loss) on derivatives	(2,746)		(3,140)
Total other comprehensive income (loss)	(5,289)	(49,289)	39,346	(53,492)
Total Comprehensive Income (Loss)	90,569	(119,545)	252,107	(10,354)
Less: Comprehensive Income Attributable to Noncontrolling Interests	323	670	841	1,295
Comprehensive Income (Loss) Attributable to RPM International Inc. Stockholders	$ 90,246	$ (120,215)	$ 251,266	$ (11,649)