Change in Projected Benefit Obligation/Accumulated Postretirement Benefit Obligation (Detail) (USD $) In Millions, unless otherwise specified	0 Months Ended	12 Months Ended
	Oct. 19, 2012	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Recognized in Consolidated Balance Sheets:
Noncurrent asset		$ (23)	$ 0
Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation-beginning of fiscal year		839	743
Service cost		38	41	45
Interest cost		40	38	40
Actuarial loss (gain)		132	77
Benefit payments		(60)	(63)
Settlements		1	3
Benefit obligation-end of fiscal year		990	839	743
Accumulated benefit obligation		982	839
Change in Plan Assets:
Balance at October 1		783	766
Actual return on plan assets		166	10
Company contribution		84	70
Benefit payments		(60)	(63)
Balance at September 30		973	783	766
Funded status at end of fiscal year		(17)	(56)
Recognized in Consolidated Balance Sheets:
Noncurrent asset		(23)	0
Current liability		(8)	(4)
Noncurrent liability		(32)	(52)
Funded status at end of fiscal year		(17)	(56)
Other Postretirement Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation-beginning of fiscal year		38	34
Service cost	0	0	0	0
Interest cost	1	1	1	1
Actuarial loss (gain)		(3)	7
Benefit payments		(4)	(4)
Settlements		0	0
Benefit obligation-end of fiscal year		32	38	34
Change in Plan Assets:
Balance at October 1		0	0
Actual return on plan assets		0	0
Company contribution		4	4
Benefit payments		(4)	(4)
Balance at September 30		0	0	0
Funded status at end of fiscal year		(32)	(38)
Recognized in Consolidated Balance Sheets:
Noncurrent asset		0	0
Current liability		(4)	(4)
Noncurrent liability		(28)	(34)
Funded status at end of fiscal year		$ (32)	$ (38)