Asset Retirement Obligations (Schedule of Fair Value Assumptions) (Details)
6 Months Ended
Feb. 28, 2014
Feb. 28, 2013
Credit adjusted risk free interest rate 8.00% 11.20%
Minimum [Member]
   
Inflation rate 3.90% 3.90%
Estimated asset life 20 years 24 years
Maximum [Member]
   
Inflation rate 4.00% 4.00%
Estimated asset life 40 years 27 years 7 months 6 days