Summary of Changes in Total Equity, Shareholders' Equity Attributable to Controlling Interest, and Equity Attributable to Noncontrolling Interest (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2014	Nov. 30, 2013	Nov. 30, 2014	Nov. 30, 2013
Beginning Balance			$ 944,882
Net earnings	31,455	28,340	80,275	84,693
Other comprehensive loss	(9,151)	3,390	(17,782)	6,255
Common shares issued, net of withholding tax			(454)
Common shares in NQ plans			14,227
Stock-based compensation			16,628
Purchases and retirement of common shares			(41,620)
Cash dividends declared			(24,553)
Acquisition of dHybrid Systems, LLC			4,082
Dividend to noncontrolling interest			(4,677)
Ending Balance	971,008		971,008
Additional Paid-in Capital
Beginning Balance			262,610
Common shares issued, net of withholding tax			(454)
Common shares in NQ plans			14,227
Stock-based compensation			16,628
Purchases and retirement of common shares			(4,350)
Ending Balance	288,661		288,661
Cumulative Other Comprehensive Income (Loss), Net of Tax
Beginning Balance			(3,581)
Other comprehensive loss			(16,168)
Ending Balance	(19,749)		(19,749)
Retained Earnings
Beginning Balance			591,783
Net earnings			73,630
Purchases and retirement of common shares			(37,270)
Cash dividends declared			(24,553)
Ending Balance	603,590		603,590
Parent
Beginning Balance			850,812
Net earnings			73,630
Other comprehensive loss			(16,168)
Common shares issued, net of withholding tax			(454)
Common shares in NQ plans			14,227
Stock-based compensation			16,628
Purchases and retirement of common shares			(41,620)
Cash dividends declared			(24,553)
Ending Balance	872,502		872,502
Noncontrolling Interest
Beginning Balance			94,070
Net earnings			6,645
Other comprehensive loss			(1,614)
Acquisition of dHybrid Systems, LLC			4,082
Dividend to noncontrolling interest			(4,677)
Ending Balance	$ 98,506		$ 98,506