Changes in Equity - Summary of Changes in Equity by Component and in Total (Detail) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Feb. 29, 2020	Nov. 30, 2019	Aug. 31, 2019	Feb. 28, 2019	Nov. 30, 2018	Aug. 31, 2018	Feb. 29, 2020	Feb. 28, 2019
Balance	$ 958,743	$ 907,442	$ 948,394	$ 986,255	$ 1,037,374	$ 1,036,375	$ 948,394	$ 1,036,375
Net earnings (loss)	18,888	56,922	(2,455)	29,548	37,792	56,958
Other comprehensive income (loss)	1,721	9,970	3,156	917	(11,300)	(5,762)	14,847	(16,145)
Consolidation of Samuel	24,269
Common shares issued, net of withholding tax	429	(3,811)	(3,213)	104	(658)	(4,091)
Common shares in NQ plans	108	239	74	80	306	152
Stock-based compensation	2,834	2,880	4,545	1,947	3,730	4,838
Purchases and retirement of common shares	(21,373)		(29,599)	(28,587)	(63,581)	(36,852)
Cash dividends declared	(13,426)	(13,446)	(13,460)	(13,256)	(13,401)	(13,668)
Dividends to noncontrolling interest		(1,453)			(4,007)	(2,320)
Balance	972,193	958,743	907,442	977,008	986,255	1,037,374	972,193	977,008
Accounting Standards Update 2014-09
ASC 606 transition adjustment						1,744
Additional Paid-in Capital
Balance	280,077	280,769	283,177	288,326	292,488	295,592	283,177	295,592
Net earnings (loss)	0	0	0	0	0	0
Other comprehensive income (loss)	0	0	0	0	0	0
Consolidation of Samuel	0
Common shares issued, net of withholding tax	429	(3,811)	(3,213)	104	(658)	(4,091)
Common shares in NQ plans	108	239	74	80	306	152
Stock-based compensation	2,834	2,880	4,545	1,947	3,730	4,838
Purchases and retirement of common shares	(2,812)		(3,814)	(4,061)	(7,540)	(4,003)
Cash dividends declared	0	0	0	0	0	0
Dividends to noncontrolling interest		0			0	0
Balance	280,636	280,077	280,769	286,396	288,326	292,488	280,636	286,396
Additional Paid-in Capital | Accounting Standards Update 2014-09
ASC 606 transition adjustment						0
AOCI Attributable to Parent
Balance	(30,338)	(40,308)	(43,464)	(31,570)	(20,325)	(14,580)	(43,464)	(14,580)
Net earnings (loss)	0	0	0	0	0	0
Other comprehensive income (loss)	1,721	9,970	3,156	889	(11,245)	(5,745)
Consolidation of Samuel	0
Common shares issued, net of withholding tax	0	0	0	0	0	0
Common shares in NQ plans	0	0	0	0	0	0
Stock-based compensation	0	0	0	0	0	0
Purchases and retirement of common shares	0		0	0	0	0
Cash dividends declared	0	0	0	0	0	0
Dividends to noncontrolling interest		0			0	0
Balance	(28,617)	(30,338)	(40,308)	(30,681)	(31,570)	(20,325)	(28,617)	(30,681)
AOCI Attributable to Parent | Accounting Standards Update 2014-09
ASC 606 transition adjustment						0
Retained Earnings
Balance	586,152	547,512	591,533	611,916	647,356	637,757	591,533	637,757
Net earnings (loss)	15,311	52,086	(4,776)	26,773	34,002	54,942
Other comprehensive income (loss)	0	0	0	0	0	0
Consolidation of Samuel	0
Common shares issued, net of withholding tax	0	0	0	0	0	0
Common shares in NQ plans	0	0	0	0	0	0
Stock-based compensation	0	0	0	0	0	0
Purchases and retirement of common shares	(18,561)		(25,785)	(24,526)	(56,041)	(32,849)
Cash dividends declared	(13,426)	(13,446)	(13,460)	(13,256)	(13,401)	(13,668)
Dividends to noncontrolling interest		0			0	0
Balance	569,476	586,152	547,512	600,907	611,916	647,356	569,476	600,907
Retained Earnings | Accounting Standards Update 2014-09
ASC 606 transition adjustment						1,174
Parent
Balance	835,891	787,973	831,246	868,672	919,519	918,769	831,246	918,769
Net earnings (loss)	15,311	52,086	(4,776)	26,773	34,002	54,942
Other comprehensive income (loss)	1,721	9,970	3,156	889	(11,245)	(5,745)
Consolidation of Samuel	0
Common shares issued, net of withholding tax	429	(3,811)	(3,213)	104	(658)	(4,091)
Common shares in NQ plans	108	239	74	80	306	152
Stock-based compensation	2,834	2,880	4,545	1,947	3,730	4,838
Purchases and retirement of common shares	(21,373)		(29,599)	(28,587)	(63,581)	(36,852)
Cash dividends declared	(13,426)	(13,446)	(13,460)	(13,256)	(13,401)	(13,668)
Dividends to noncontrolling interest		0			0	0
Balance	821,495	835,891	787,973	856,622	868,672	919,519	821,495	856,622
Parent | Accounting Standards Update 2014-09
ASC 606 transition adjustment						1,174
Noncontrolling Interest
Balance	122,852	119,469	117,148	117,583	117,855	117,606	117,148	117,606
Net earnings (loss)	3,577	4,836	2,321	2,775	3,790	2,016
Other comprehensive income (loss)	0	0	0	28	(55)	(17)
Consolidation of Samuel	24,269
Common shares issued, net of withholding tax	0	0	0	0	0	0
Common shares in NQ plans	0	0	0	0	0	0
Stock-based compensation	0	0	0	0	0	0
Purchases and retirement of common shares	0		0	0	0	0
Cash dividends declared	0	0	0	0	0	0
Dividends to noncontrolling interest		(1,453)			(4,007)	(2,320)
Balance	$ 150,698	$ 122,852	$ 119,469	$ 120,386	$ 117,583	117,855	$ 150,698	$ 120,386
Noncontrolling Interest | Accounting Standards Update 2014-09
ASC 606 transition adjustment						$ 570