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v3.25.3

Share-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions |  | 12 Months Ended
--- | --- | ---
Mar. 13, 2025 | Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2023
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |
Percentage of vesting in first anniversary |  | 30.00% |  |
Percentage of vesting in second anniversary |  | 30.00% |  |
Percentage of vesting in third anniversary |  | 40.00% |  |
Net share-based compensation expense |  | $ 22 | $ 23 | $ 18
Stock Options [Member] |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |
Percentage of exercise price equal to market price on the date of grant |  | 100.00% |  |
Vesting period (in years) |  | 3 years |  |
Expiration period, years |  | 10 years |  |
Unrecognized compensation cost |  | $ 3 |  |
Weighted-average period, years |  | 1 year |  |
Options outstanding, aggregate intrinsic value |  | $ 23 |  |
Intrinsic value of options exercised |  | 6 | 17 | 2
Cash received from exercises |  | 9 | 20 | $ 4
Tax benefits from the exercise of stock options |  | $ 1 | $ 2 |
Stock Options, Weighted Average Grant Date Fair Value, Granted |  | $ 44.96 | $ 27.42 | $ 26.28
Restricted Stock Units [Member] |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |
Vesting period (in years) |  | 3 years |  |
Unrecognized compensation cost |  | $ 21 |  |
Weighted-average period, years |  | 1 year |  |
Estimated weighted average grant date fair value |  | $ 110.67 | $ 75.98 | $ 73.68
Intrinsic value of restricted stock units vested |  | $ 32 | $ 37 | $ 20
Restricted Stock [Member] |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |
Vesting period (in years) |  | 3 years |  |
Supplemental 401(k) Plan [Member] |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |
Supplemental retirement savings plan, aggregate value of the accounts, shares |  | 110,000 | 117,000 |
2025 Long-Term Incentive Plan [Member] | Maximum [Member] |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |
Common stock, additional shares authorized | 1,400,000 |  |  |

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