Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Aug. 31, 2018	Aug. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net Income	$ 70,186	$ 116,903
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(40,689)	44,478
Pension and other postretirement benefit liability adjustments (net of tax of $982 and $646, respectively)	3,056	629
Unrealized gain (loss) on securities (net of tax of $668 and $(149), respectively)	2,476	(78)
Unrealized gain (loss) on derivatives	921	(394)
Total other comprehensive income (loss) income	(34,236)	44,635
Total Comprehensive Income	35,950	161,538
Less: Comprehensive Income Attributable to Noncontrolling Interests	164	518
Comprehensive Income Attributable to RPM International Inc. Stockholders	$ 35,786	$ 161,020