Amounts from Accumulated Other Comprehensive Income to be Amortized into Net Periodic Benefit Cost (Detail) $ in Millions	12 Months Ended
Sep. 30, 2015 USD ($)
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actuarial loss (gain)	$ 14
Prior service credit	(7)
Total	7
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actuarial loss (gain)	(1)
Prior service credit	(3)
Total	$ (4)

Amount included in accumulated other comprehensive income (AOCI) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position, including gain (loss), prior service cost (credit), and transition asset (obligation).

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration