Property and Equipment - Components of Property and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Aug. 31, 2013	Aug. 31, 2012
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 377,045	$ 365,389
Accumulated depreciation	(264,904)	(252,198)
Net property and equipment	112,141	113,191
Land and land improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	11,881	11,623
Plant and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	359,909	346,087
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 5,255	$ 7,679