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Benefit Plans Other Postemployment Benefits (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2018
Other Post-Employment Benefits |  |  |  |
Discount rate |  | 0.69% | 1.68% | 3.05%
Period expense |  | $ 45 | $ 59 | $ 6
Postemployment benefits liability |  |  | 419 | $ 339
Payment of Workers Compensation Claims | $ 32 | 74 | 39 |
Accounts Payable and Accrued Liabilities |  |  |  |
Other Post-Employment Benefits |  |  |  |
Postemployment Benefits Liability, Current |  | 0 | 36 |
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent |  |  |  |
Other Post-Employment Benefits |  |  |  |
Postemployment benefits liability, noncurrent |  | $ 390 | $ 383 |

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