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Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions | 9 Months Ended |  |
--- | --- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jul. 31, 2018 | Jan. 31, 2015
Class Of Stock [Line Items] |  |  |  |
Repurchase authorization, shares |  |  |  | 5,000,000
Cash dividends paid to common stockholders | $ 60 | $ 57 |  |
Cash dividend paid per share | $ 0.96 | $ 0.915 |  |
Dividends paid to noncontrolling interests | $ 21 | $ 13 |  |
Subsequent Event [Member] |  |  |  |
Class Of Stock [Line Items] |  |  |  |
Repurchase authorization, shares |  |  | 10,000,000 |
January 2015 Share Repurchase Authorization [Member] |  |  |  |
Class Of Stock [Line Items] |  |  |  |
Common stock shares repurchased under the current authorization | 4,171,802 |  |  |
Shares remaining available for repurchase under the current authorization | 828,198 |  |  |

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