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Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)
12 Months Ended
Aug. 31, 2012
Aug. 31, 2011
Aug. 31, 2010
Schedule Of Significant Accounting Policies [Line Items]      
Sales of by-products that reduced cost of goods sold $ 70,000,000 $ 56,800,000 $ 38,700,000
Intangible assets with indefinite lives 0    
Depreciation of assets 14,127,000 14,415,000 14,791,000
Interest capitalized 48,000 0 0
Minimum percentage likelihood of tax benefit to be realized 50.00%    
Research and development costs expensed 5,838,000 4,772,000 4,371,000
Foreign currency transaction gain (loss)     400,000
Eco Energy, Inc [Member]
     
Schedule Of Significant Accounting Policies [Line Items]      
Entity-Wide Revenue, Major Customer (in percentage) 28.00% 34.00% 27.00%
Export Distribution Channel [Member]
     
Schedule Of Significant Accounting Policies [Line Items]      
Export sales as a percentage of total sales (in percentage) 9.00% 9.00% 9.00%
Real estate [Member]
     
Schedule Of Significant Accounting Policies [Line Items]      
Depreciation of assets $ 12,700,000 $ 12,800,000 $ 13,100,000
Minimum [Member] | Equipment And Vehicles [Member]
     
Schedule Of Significant Accounting Policies [Line Items]      
Average useful life (in years) 3 years    
Minimum [Member] | Real estate [Member]
     
Schedule Of Significant Accounting Policies [Line Items]      
Average useful life (in years) 12 years    
Maximum [Member] | Equipment And Vehicles [Member]
     
Schedule Of Significant Accounting Policies [Line Items]      
Average useful life (in years) 12 Years    
Maximum [Member] | Real estate [Member]
     
Schedule Of Significant Accounting Policies [Line Items]      
Average useful life (in years) 46 years    
Patents [Member]
     
Schedule Of Significant Accounting Policies [Line Items]      
Weighted average remaining amortization period (in years) 4 years    
Paper Industry [Member] | Customer Concentration Risk [Member] | Sales Revenue, Goods, Net [Member]
     
Schedule Of Significant Accounting Policies [Line Items]      
Concentration of sales (in percentage) 43.00% 40.00% 45.00%
Number of customers in paper industry primarily responsible for increase in allowance for doubtful accounts (in customers) 2