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Earnings Per Share - Additional Information (Detail) - $ / shares
3 Months Ended 6 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Mar. 31, 2019
Mar. 31, 2018
Earnings Per Share [Abstract]        
Dividend declared $ 0.26 $ 0.26 $ 0.52 $ 0.52