Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Aug. 31, 2017	Aug. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net Income	$ 116,903	$ 113,394
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	44,478	(11,511)
Pension and other postretirement benefit liability adjustments (net of tax of $646; $2,799, respectively)	629	5,704
Unrealized (loss) gain on securities (net of tax of $(149); $1,096, respectively)	(78)	1,604
Unrealized (loss) on derivatives	(394)
Total other comprehensive income (loss)	44,635	(4,203)
Total Comprehensive Income	161,538	109,191
Less: Comprehensive Income Attributable to Noncontrolling Interests	518	625
Comprehensive Income Attributable to RPM International Inc. Stockholders	$ 161,020	$ 108,566