Deferred Tax Assets and Liabilities Classified in Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	May. 31, 2015	May. 31, 2014
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred income taxes, current assets	$ 22,034	$ 24,272
Other assets, noncurrent assets	1,173	4
Deferred income taxes, noncurrent liabilities	(21,495)	(71,333)
Net deferred tax asset (liability)	$ 1,712	$ (47,057)