Debt (Long-term Debt) (Details) - USD ($)
$ in Millions |
6 Months Ended |
|
|
|
|
Mar. 31, 2016 |
Mar. 31, 2015 |
Sep. 30, 2015 |
Jun. 30, 2015 |
Mar. 31, 2014 |
Jan. 31, 2010 |
| Long-term Debt |
|
|
|
|
|
|
|
| Principal amount of notes |
|
$ 1,683
|
|
$ 1,680
|
|
|
|
| Fair value, swap adjustment |
|
37
|
|
34
|
|
|
|
| Current portion of long-term debt |
|
300
|
|
0
|
|
|
|
| Long-term Debt, Excluding Current Maturities |
|
1,383
|
|
1,680
|
|
|
|
| Interest Paid |
|
$ 28
|
$ 27
|
|
|
|
|
| 2043 Notes [Member] | Unsecured Notes [Member] |
|
|
|
|
|
|
|
| Long-term Debt |
|
|
|
|
|
|
|
| Interest rate |
|
4.80%
|
|
|
|
|
|
| Principal amount of notes |
|
$ 398
|
|
398
|
|
|
|
| 2023 Notes [Member] | Unsecured Notes [Member] |
|
|
|
|
|
|
|
| Long-term Debt |
|
|
|
|
|
|
|
| Interest rate |
|
3.70%
|
|
|
|
|
|
| Principal amount of notes |
|
$ 399
|
|
399
|
|
|
|
| Derivative basis spread on variable rate |
|
|
|
|
|
0.94%
|
|
| 2021 Notes [Member] | Unsecured Notes [Member] |
|
|
|
|
|
|
|
| Long-term Debt |
|
|
|
|
|
|
|
| Interest rate |
|
3.10%
|
|
|
|
|
|
| Principal amount of notes |
|
$ 250
|
|
250
|
|
|
|
| 2019 Notes [Member] | Unsecured Notes [Member] |
|
|
|
|
|
|
|
| Long-term Debt |
|
|
|
|
|
|
|
| Interest rate |
|
5.25%
|
|
|
|
|
|
| Principal amount of notes |
|
$ 299
|
|
299
|
|
|
|
| Derivative basis spread on variable rate |
|
|
|
|
3.56%
|
|
1.235%
|
| 2016 Notes [Member] | Unsecured Notes [Member] |
|
|
|
|
|
|
|
| Long-term Debt |
|
|
|
|
|
|
|
| Principal amount of notes |
|
$ 300
|
|
$ 300
|
|
|
|
| Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate |
|
0.63%
|
|
|
|
|
|
| Three month LIBOR [Member] | 2016 Notes [Member] | Unsecured Notes [Member] |
|
|
|
|
|
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| Long-term Debt |
|
|
|
|
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| Derivative basis spread on variable rate |
[1] |
0.35%
|
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