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Commitments and Contingencies - Changes to Environmental Liabilities (Details) - USD ($)
$ in Thousands
6 Months Ended
Feb. 29, 2020
Feb. 23, 2019
Accrual For Environmental Loss Contingencies Roll Forward    
Beginning balance $ 27,718  
Revisions in estimates 1,200  
Costs incurred for which reserves have been provided (627)  
Insurance proceeds 62  
Accretion on environmental contingencies 269 $ 377
Changes in discount rates 781  
Ending balance $ 29,403