Changes in Equity - Summary of Changes in Equity by Component and in Total (Detail) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Nov. 30, 2018	Aug. 31, 2018	Nov. 30, 2017	Aug. 31, 2017	Nov. 30, 2018	Nov. 30, 2017
Beginning Balance	$ 1,037,374	$ 1,036,375	$ 1,082,727	$ 1,073,929	$ 1,036,375	$ 1,073,929
Net earnings	37,792	56,958	41,622	48,074	94,750	89,696
Other comprehensive income (loss)	(11,300)	(5,762)	(699)	17,753	(17,062)	17,054
Common shares issued, net of withholding tax	(658)	(4,091)	(722)	(3,274)
Common shares in NQ plans	306	152	350	536
Stock-based compensation	3,730	4,838	3,169	4,822
Purchases and retirement of common shares	(63,581)	(36,852)	(67,448)	(45,076)
Cash dividends declared	(13,401)	(13,668)	(13,020)	(13,317)
Dividends to noncontrolling interest	(4,007)	(2,320)	(3,196)	(720)
Ending Balance	986,255	1,037,374	1,042,783	1,082,727	986,255	1,042,783
Accounting Standards Update 2014-09
ASC 606 transition adjustment		1,744
Additional Paid-in Capital
Beginning Balance	292,488	295,592	301,240	303,391	295,592	303,391
Common shares issued, net of withholding tax	(658)	(4,091)	(722)	(3,274)
Common shares in NQ plans	306	152	350	536
Stock-based compensation	3,730	4,838	3,169	4,822
Purchases and retirement of common shares	(7,540)	(4,003)	(7,245)	(4,235)
Ending Balance	288,326	292,488	296,792	301,240	288,326	296,792
AOCI Attributable to Parent
Beginning Balance	(20,325)	(14,580)	(10,461)	(27,775)	(14,580)	(27,775)
Other comprehensive income (loss)	(11,245)	(5,745)	(619)	17,314
Ending Balance	(31,570)	(20,325)	(11,080)	(10,461)	(31,570)	(11,080)
Retained Earnings
Beginning Balance	647,356	637,757	667,395	676,019	637,757	676,019
Net earnings	34,002	54,942	39,403	45,534
Purchases and retirement of common shares	(56,041)	(32,849)	(60,203)	(40,841)
Cash dividends declared	(13,401)	(13,668)	(13,020)	(13,317)
Ending Balance	611,916	647,356	633,575	667,395	611,916	633,575
Retained Earnings | Accounting Standards Update 2014-09
ASC 606 transition adjustment		1,174
Parent
Beginning Balance	919,519	918,769	958,174	951,635	918,769	951,635
Net earnings	34,002	54,942	39,403	45,534
Other comprehensive income (loss)	(11,245)	(5,745)	(619)	17,314
Common shares issued, net of withholding tax	(658)	(4,091)	(722)	(3,274)
Common shares in NQ plans	306	152	350	536
Stock-based compensation	3,730	4,838	3,169	4,822
Purchases and retirement of common shares	(63,581)	(36,852)	(67,448)	(45,076)
Cash dividends declared	(13,401)	(13,668)	(13,020)	(13,317)
Ending Balance	868,672	919,519	919,287	958,174	868,672	919,287
Parent | Accounting Standards Update 2014-09
ASC 606 transition adjustment		1,174
Noncontrolling Interest
Beginning Balance	117,855	117,606	124,553	122,294	117,606	122,294
Net earnings	3,790	2,016	2,219	2,540
Other comprehensive income (loss)	(55)	(17)	(80)	439
Dividends to noncontrolling interest	(4,007)	(2,320)	(3,196)	(720)
Ending Balance	$ 117,583	117,855	$ 123,496	$ 124,553	$ 117,583	$ 123,496
Noncontrolling Interest | Accounting Standards Update 2014-09
ASC 606 transition adjustment		$ 570