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Share Repurchase Plan (Narrative) (Details) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 15 Months Ended
Nov. 30, 2019
Nov. 30, 2018
Nov. 30, 2019
Equity, Class of Treasury Stock [Line Items]      
Total cost of repurchased shares $ 4,957 $ 6,863  
2018 To 2020 Share Repurchase Program [Member]      
Equity, Class of Treasury Stock [Line Items]      
Share buy-back plan, amount authorized $ 75,000   $ 75,000
Share buy-back plan, number of shares repurchased 26,800   202,755
Average price of shares repurchased $ 184.92    
Total cost of repurchased shares $ 5,000   $ 34,600
Maximum [Member] | 2018 To 2020 Share Repurchase Program [Member]      
Equity, Class of Treasury Stock [Line Items]      
Share buy-back plan, amount authorized $ 75,000   $ 75,000