Shareholders' Equity (Common Stock Transactions) (Details) (USD $)
In Thousands, except Share data, unless otherwise specified
6 Months Ended
Feb. 28, 2014
Aug. 31, 2013
Classes of stock    
Preferred stock, shares authorized 10,000,000 10,000,000
Preferred stock, par value $ 0.01 $ 0.01
Preferred stock, shares issued 0 0
Preferred stock, shares outstanding 0 0
Common stock, shares authorized 100,000,000 100,000,000
Common stock, par value $ 0.001 $ 0.001
Common stock, shares issued 76,685,709 70,587,723
Common stock, shares outstanding 76,685,709 70,587,723
Common stock issued for acquisition of mineral interests    
Number of common shares issued for mineral property leases 243,179  
Number of common shares issued for acquisitions 851,857  
Total common shares issued 1,095,036  
Average price per common share $ 9.24  
Aggregate value of shares issued $ 10,122