Amounts Recognized in Accumulated Comprehensive Income Before Tax (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net actuarial loss (gain)	$ 108	$ 328
Prior service credit	(23)	(33)
Total	85	295
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net actuarial loss (gain)	(6)	(3)
Prior service credit	(11)	(14)
Total	$ (17)	$ (17)