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Earnings per Share and Dividends per Share - Additional Information (Detail) - $ / shares
3 Months Ended 6 Months Ended
Mar. 06, 2020
Mar. 31, 2020
Mar. 31, 2019
Mar. 31, 2020
Mar. 31, 2019
Weighted Average Amounts Used In Calculating Earnings Per Share [Line Items]          
Dividends paid $ 0.1375        
Restricted Stock Units (RSUs) [Member]          
Weighted Average Amounts Used In Calculating Earnings Per Share [Line Items]          
Stock options excluded from diluted earnings per share   184,871 280,683 184,871 323,432