Settlement Guarantee Management - Additional Information (Detail) $ in Millions |
12 Months Ended | |
|---|---|---|
|
Sep. 30, 2015
USD ($)
month
|
Sep. 30, 2014
USD ($)
|
|
| Settlement Guarantee Management [Abstract] | ||
| Number of Rolling Months of Average Chargebacks Volume Included in Settlement Risk Exposure | month | 4 | |
| Estimated maximum settlement exposure | $ 43,500 | $ 56,900 |
| Covered settlement exposure | 2,200 | 3,200 |
| Estimated probability-weighted value of the guarantee | $ 1 | $ 2 |