| **Income Taxes - Income Tax (Details) (USD $)In Millions, unless otherwise specified** | 3 Months Ended | 6 Months Ended | 3 Months Ended |        |        | 3 Months Ended |
|----------------------------------------------------------------------------------------|----------------|----------------|----------------|--------|--------|----------------|
||
| **Income Taxes [Line Items]**                                                          |           |           |           |   |   |           |   |   |
| Income Tax Expense (Benefit)                                                           | $ 23           | $ 22           | $ 11           | $ 37   |   |           |   | $ (13) |
| Deferred Tax Assets, Valuation Allowance                                               | 29             |           |           |   |   |           |   |   |
| Income Taxes Percent Likelihood Of Being Realized Upon Settlement                      | 50.00%         |           | 50.00%         |   |   |           |   |   |
| Liability for uncertain tax positions                                                  | 63             |           | 63             |   |   |           |   |   |
| Unrecognized tax benefits that would not impact effective tax rate                     | 7              |           | 7              |   |   |           |   |   |
| Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense                   | 1              |           | (2)            |   |   |           |   |   |
| Liability for Uncertain Tax Benefits term range                                        |           |           | 12 days        |   |   |           |   |   |
| Liability for Uncertain Tax Positions                                                  |           |           |           |   |   | 8              | 12 |   |
| Tax Adjustments, Settlements, and Unusual Provisions                                   |           |           |           |   | $ 4    |           |   |   |

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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Income Taxes Percent Likelihood Of Being Realized Upon Settlement
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| - Definition
Liability for Uncertain Tax Benefits Time Range
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| - Definition
Unrecognized Tax Benefits that Would Not Impact Effective Tax Rate
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.
+ References
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The current portion of the amount recognized for uncertain tax positions as of the balance sheet date.
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of increase (decrease) to previously recorded tax expense. Includes, but is not limited to, significant settlements of income tax disputes, and unusual tax positions or infrequent actions taken by the entity, including tax assessment reversal, and IRS tax settlement.
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of expense for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.
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| - Definition
The amount of the change in the period in the valuation allowance for a specified deferred tax asset.
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