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, 2020	Aug. 31, 2020	Nov. 30, 2019	Aug. 31, 2019	Nov. 30, 2020	Nov. 30, 2019
Balance	$ 1,529,900	$ 966,433	$ 907,442	$ 948,394	$ 966,433	$ 948,394
Net earnings (loss)	(68,512)	618,738	56,922	(2,455)
Other comprehensive income	14,163	11,242	9,970	3,156	25,406	13,126
Common shares issued, net of withholding tax	2,294	(1,150)	(3,811)	(3,213)
Common shares in NQ plans	292	90	239	74
Stock-based compensation	3,499	3,022	2,880	4,545
Purchases and retirement of common shares	(38,563)	(54,320)	0	(29,599)
Contribution to Samuel joint venture	925
Cash dividends declared	(13,527)	(13,595)	(13,446)	(13,460)
Dividends to noncontrolling interest		(560)	(1,453)
Balance	1,430,471	1,529,900	958,743	907,442	1,430,471	958,743
Additional Paid-in Capital
Balance	278,202	283,776	280,769	283,177	283,776	283,177
Net earnings (loss)	0	0	0	0
Other comprehensive income	0	0	0	0
Common shares issued, net of withholding tax	2,294	(1,150)	(3,811)	(3,213)
Common shares in NQ plans	292	90	239	74
Stock-based compensation	3,499	3,022	2,880	4,545
Purchases and retirement of common shares	(4,486)	(7,536)	0	(3,814)
Contribution to Samuel joint venture	0
Cash dividends declared	0	0	0	0
Dividends to noncontrolling interest		0	0
Balance	279,801	278,202	280,077	280,769	279,801	280,077
Accumulated Other Comprehensive Loss, Net of Tax
Balance	(23,975)	(35,217)	(40,308)	(43,464)	(35,217)	(43,464)
Net earnings (loss)	0	0	0	0
Other comprehensive income	14,163	11,242	9,970	3,156
Common shares issued, net of withholding tax	0	0	0	0
Common shares in NQ plans	0	0	0	0
Stock-based compensation	0	0	0	0
Purchases and retirement of common shares	0	0	0	0
Contribution to Samuel joint venture	0
Cash dividends declared	0	0	0	0
Dividends to noncontrolling interest		0	0
Balance	(9,812)	(23,975)	(30,338)	(40,308)	(9,812)	(30,338)
Retained Earnings
Balance	1,128,558	572,262	547,512	591,533	572,262	591,533
Net earnings (loss)	(74,044)	616,675	52,086	(4,776)
Other comprehensive income	0	0	0	0
Common shares issued, net of withholding tax	0	0	0	0
Common shares in NQ plans	0	0	0	0
Stock-based compensation	0	0	0	0
Purchases and retirement of common shares	(34,077)	(46,784)	0	(25,785)
Contribution to Samuel joint venture	0
Cash dividends declared	(13,527)	(13,595)	(13,446)	(13,460)
Dividends to noncontrolling interest		0	0
Balance	1,006,910	1,128,558	586,152	547,512	1,006,910	586,152
Parent
Balance	1,382,785	820,821	787,973	831,246	820,821	831,246
Net earnings (loss)	(74,044)	616,675	52,086	(4,776)
Other comprehensive income	14,163	11,242	9,970	3,156
Common shares issued, net of withholding tax	2,294	(1,150)	(3,811)	(3,213)
Common shares in NQ plans	292	90	239	74
Stock-based compensation	3,499	3,022	2,880	4,545
Purchases and retirement of common shares	(38,563)	(54,320)	0	(29,599)
Contribution to Samuel joint venture	0
Cash dividends declared	(13,527)	(13,595)	(13,446)	(13,460)
Dividends to noncontrolling interest		0	0
Balance	1,276,899	1,382,785	835,891	787,973	1,276,899	835,891
Noncontrolling Interest
Balance	147,115	145,612	119,469	117,148	145,612	117,148
Net earnings (loss)	5,532	2,063	4,836	2,321
Other comprehensive income	0	0	0	0
Common shares issued, net of withholding tax	0	0	0	0
Common shares in NQ plans	0	0	0	0
Stock-based compensation	0	0	0	0
Purchases and retirement of common shares	0	0	0	0
Contribution to Samuel joint venture	925
Cash dividends declared	0	0	0	0
Dividends to noncontrolling interest		(560)	(1,453)
Balance	$ 153,572	$ 147,115	$ 122,852	$ 119,469	$ 153,572	$ 122,852