Changes in Equity (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Aug. 31, 2013	Aug. 31, 2012
Beginning Balance	$ 872,237
Net earnings	56,353	34,865
Other comprehensive income (loss)	2,865	4,720
Common shares issued	2,201
Stock-based compensation	7,230
Purchases and retirement of common shares	(30,516)
Cash dividends declared	(10,588)
Dividend paid to noncontrolling interest	(1,763)
Acquisition of TWB	72,369
Ending Balance	970,388
Additional Paid-in Capital
Beginning Balance	244,864
Common shares issued	2,201
Stock-based compensation	7,230
Purchases and retirement of common shares	(3,104)
Ending Balance	251,191
Accumulated Other Comprehensive Income (Loss)
Beginning Balance	(12,036)
Other comprehensive income (loss)	3,882
Ending Balance	(8,154)
Retained Earnings
Beginning Balance	597,994
Net earnings	54,557
Purchases and retirement of common shares	(27,412)
Cash dividends declared	(10,588)
Ending Balance	614,551
Parent
Beginning Balance	830,822
Net earnings	54,557
Other comprehensive income (loss)	3,882
Common shares issued	2,201
Stock-based compensation	7,230
Purchases and retirement of common shares	(30,516)
Cash dividends declared	(10,588)
Ending Balance	857,588
Noncontrolling Interest
Beginning Balance	41,415
Net earnings	1,796
Other comprehensive income (loss)	(1,017)
Dividend paid to noncontrolling interest	(1,763)
Acquisition of TWB	72,369
Ending Balance	$ 112,800