|
Components of Net Periodic Benefit Cost (Detail) (USD $)
In Millions, unless otherwise specified |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
|
Mar. 31, 2015
|
Mar. 31, 2014
|
Mar. 31, 2015
|
Mar. 31, 2014
|
|
| Pension Benefits | ||||
| Defined Benefit Plan Disclosure [Line Items] | ||||
| Service cost | $ 11 | $ 12 | $ 23 | $ 23 |
| Interest cost | 10 | 11 | 20 | 21 |
| Expected return on assets | (18) | (17) | (36) | (34) |
| Amortization of prior service credit | (1) | (2) | (3) | (4) |
| Curtailment gain | 0 | (3) | 0 | (3) |
| Settlement loss | 2 | 0 | 4 | 1 |
| Total net periodic benefit cost | 4 | 1 | 8 | 4 |
| Other Postretirement Benefits | ||||
| Defined Benefit Plan Disclosure [Line Items] | ||||
| Service cost | 0 | 0 | 0 | 0 |
| Interest cost | 0 | 0 | 0 | 0 |
| Expected return on assets | 0 | 0 | 0 | 0 |
| Amortization of prior service credit | (1) | (1) | (2) | (2) |
| Curtailment gain | 0 | 0 | 0 | 0 |
| Settlement loss | 0 | 0 | 0 | 0 |
| Total net periodic benefit cost | $ (1) | $ (1) | $ (2) | $ (2) |