Change in Projected Benefit Obligation/Accumulated Postretirement Benefit Obligation (Detail) (USD $) In Millions	12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Change in Plan Assets:
Fair value of plan assets-end of fiscal year	$ 783	$ 780
Recognized in Consolidated Balance Sheets:
Non-current asset		53
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation-beginning of fiscal year	743	739
Service cost	41	45
Interest cost	38	40
Plan amendments		(12)
Actuarial loss (gain)	77	3
Benefit payments	(63)	(72)
Settlements	3
Benefit obligation-end of fiscal year	839	743
Accumulated benefit obligation	839	743
Change in Plan Assets:
Fair value of plan assets-beginning of fiscal year	766	703
Actual return on plan assets	10	73
Company contribution	70	62
Benefit payments	(63)	(72)
Fair value of plan assets-end of fiscal year	783	766
Funded status at end of fiscal year	(56)	23
Recognized in Consolidated Balance Sheets:
Non-current asset		53
Current liability	(4)	(10)
Non-current liability	(52)	(20)
Funded status at end of fiscal year	(56)	23
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation-beginning of fiscal year	34	43
Interest cost	1	1
Actuarial loss (gain)	7	(6)
Benefit payments	(4)	(4)
Benefit obligation-end of fiscal year	38	34
Change in Plan Assets:
Company contribution	4	4
Benefit payments	(4)	(4)
Funded status at end of fiscal year	(38)	(34)
Recognized in Consolidated Balance Sheets:
Current liability	(4)	(4)
Non-current liability	(34)	(30)
Funded status at end of fiscal year	$ (38)	$ (34)