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Income Taxes - Additional Information (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Mar. 31, 2022 | Mar. 31, 2021 | Mar. 31, 2022 | Mar. 31, 2021
Minimum [Member] |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |
Decrease in unrecognized tax benefits is reasonably possible | $ 6 |  | $ 6 |
Maximum [Member] |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |
Decrease in unrecognized tax benefits is reasonably possible | $ 16 |  | $ 16 |
Current Fiscal Year [Member] |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |
Effective tax rate (in hundredths) | 34.00% |  | 25.00% |
Tax reform (benefit) and expense | $ (7) |  | $ (5) |
Prior Fiscal Year [Member] |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |
Effective tax rate (in hundredths) |  | (26.00%) |  | (17.00%)
Tax reform (benefit) and expense |  | $ (7) |  | $ (20)

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- Definition Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32687-109319 + Details
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