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Risk Management Activities and Fair Value Measurements - Gains (Losses) on Derivative Instruments (Details) (USD $)
In Millions, unless otherwise specified |
3 Months Ended | 12 Months Ended | |||||||||||
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Sep. 30, 2013
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Sep. 30, 2012
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Jun. 30, 2013
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Cash Flow Hedging [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | |||||||||||||
| Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion) | $ 23 | $ 21 | |||||||||||
| Amount of Gain (Loss) Reclassified from AOCI into Income | 0 | [1] | (16) | [1] | |||||||||
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Cash Flow Hedging [Member] | Interest Rate Contract [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | |||||||||||||
| Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion) | 6 | 7 | |||||||||||
| Amount of Gain (Loss) Reclassified from AOCI into Income | 2 | [1] | 2 | [1] | |||||||||
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Cash Flow Hedging [Member] | Foreign Exchange Contract [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | |||||||||||||
| Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion) | 17 | 14 | |||||||||||
| Amount of Gain (Loss) Reclassified from AOCI into Income | (2) | [1] | (18) | [1] | |||||||||
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Fair Value Hedging [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | |||||||||||||
| Amount of Gain (Loss) Recognized in Income | 0 | [2] | 2 | [2] | |||||||||
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Fair Value Hedging [Member] | Interest Rate Contract [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | |||||||||||||
| Amount of Gain (Loss) Recognized in Income | (29) | [2] | 40 | [2] | |||||||||
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Fair Value Hedging [Member] | Debt [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | |||||||||||||
| Amount of Gain (Loss) Recognized in Income | 29 | [2] | (38) | [2] | |||||||||
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Net Investment Hedging [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | |||||||||||||
| Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion) | 139 | 145 | |||||||||||
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Not Designated as Hedging Instrument [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | |||||||||||||
| Amount of Gain (Loss) Recognized in Income | 109 | [3] | 281 | [3] | |||||||||
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Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | |||||||||||||
| Amount of Gain (Loss) Recognized in Income | 109 | [3],[4] | 279 | [3],[4] | |||||||||
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Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
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| Derivative Instruments, Gain (Loss) [Line Items] | |||||||||||||
| Amount of Gain (Loss) Recognized in Income | $ 0 | [3] | $ 2 | [3] | |||||||||
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