|
Income Taxes - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified |
3 Months Ended | 6 Months Ended | |||
|---|---|---|---|---|---|
|
Mar. 31, 2015
|
Mar. 31, 2014
|
Dec. 31, 2013
|
Mar. 31, 2015
|
Mar. 31, 2014
|
|
| Income Tax Disclosure [Abstract] | |||||
| Effective income tax rate reconciliation, percent | 32.00% | 22.00% | 31.00% | 27.00% | |
| Effective Income Tax Rate Reconciliation, Deduction, Qualified Production Activity from Prior Periods, Amount | $ 184 | $ 17 | $ 201 | ||
| Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit | $ 300 | $ 300 | |||