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Income Taxes - Additional Information (Detail) (USD $)
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3 Months Ended | 9 Months Ended | |||
|---|---|---|---|---|---|
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Jun. 30, 2013
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Jun. 30, 2012
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Mar. 31, 2012
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Jun. 30, 2013
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Jun. 30, 2012
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| Income Tax Disclosure [Abstract] | |||||
| Effective Income Tax Rate, Continuing Operations | 33.00% | 29.00% | 31.00% | 22.00% | |
| Tax benefit recognized related to CA apportionment rules | $ 76,000,000 | ||||
| Income Tax Impact From Remeasurement Of Deferred Taxes | 208,000,000 | ||||
| Unrecognized Tax Benefits, Period Increase (Decrease) | 10,000,000 | 231,000,000 | |||
| Unrecognized Tax Benefits that Would Impact Effective Tax Rate, Period Increase (Decrease) | 8,000,000 | 179,000,000 | |||
| Unrecognized Tax Benefits, Change in Interest on Income Taxes Accrued | 4,000,000 | 9,000,000 | 1,000,000 | 15,000,000 | |
| Increase (decrease) In Unrecognized Tax Benefits, Penalties On Income Taxes Accrued | 0 | 2,000,000 | 0 | ||
| Reclassification from deferred tax assets to income tax receivable | 1,600,000,000 | ||||
| Payments from litigation escrow account—retrospective responsibility plan (Note 2) | $ 4,383,000,000 | $ 140,000,000 | |||