Other Property - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2016	May 31, 2015	May 31, 2014
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 55,931	$ 56,445	$ 57,034
Property, Plant and Equipment, Other Types [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 1,113	$ 987	$ 1,089