Components of Total Equity and Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Aug. 31, 2018	Aug. 31, 2017
Stockholders Equity Note [Line Items]
Total equity, beginning of period	$ 1,633,538	$ 1,438,700
Net income	70,186	116,903
Other Comprehensive Income (Loss):
Foreign currency translation adjustments	(40,689)	44,478
Pension and other postretirement benefit liability adjustments, net of tax	3,056	629
Unrealized (loss) on securities, net of tax	2,476	(78)
Unrealized (loss) on derivatives, net of tax	921	(394)
Total other comprehensive income (loss) income	(34,236)	44,635
Total Comprehensive Income	35,950	161,538
Dividends paid	(42,714)	(40,089)
Other	(2,831)
Other noncontrolling interest activity		(65)
Shares repurchased and shares returned for taxes	(20,581)	(5,346)
Stock based compensation expense		7,465
Total Equity, end of period	1,613,379	1,562,203
SG&A
Other Comprehensive Income (Loss):
Stock based compensation expense	6,668
Restructuring Expense
Other Comprehensive Income (Loss):
Stock based compensation expense	3,349
Total RPM International Inc. Equity
Stockholders Equity Note [Line Items]
Total equity, beginning of period	1,630,773	1,436,061
Net income	69,764	116,416
Other Comprehensive Income (Loss):
Foreign currency translation adjustments	(40,431)	44,447
Pension and other postretirement benefit liability adjustments, net of tax	3,056	629
Unrealized (loss) on securities, net of tax	2,476	(78)
Unrealized (loss) on derivatives, net of tax	921	(394)
Total other comprehensive income (loss) income	(33,978)	44,604
Total Comprehensive Income	35,786	161,020
Dividends paid	(42,714)	(40,089)
Other	(2,834)
Shares repurchased and shares returned for taxes	(20,581)	(5,346)
Stock based compensation expense		7,465
Total Equity, end of period	1,610,447	1,559,111
Total RPM International Inc. Equity | SG&A
Other Comprehensive Income (Loss):
Stock based compensation expense	6,668
Total RPM International Inc. Equity | Restructuring Expense
Other Comprehensive Income (Loss):
Stock based compensation expense	3,349
Noncontrolling Interest
Stockholders Equity Note [Line Items]
Total equity, beginning of period	2,765	2,639
Net income	422	487
Other Comprehensive Income (Loss):
Foreign currency translation adjustments	(258)	31
Total other comprehensive income (loss) income	(258)	31
Total Comprehensive Income	164	518
Other	3
Other noncontrolling interest activity		(65)
Total Equity, end of period	$ 2,932	$ 3,092