Change in Projected Benefit Obligation/Accumulated Postretirement Benefit Obligation (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Recognized in Consolidated Balance Sheets:
Noncurrent asset	$ (192)	$ (23)
Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation-beginning of fiscal year	990	839
Service cost	43	38	41
Interest cost	35	40	38
Actuarial (gain) loss	(127)	132
Benefit payments	(44)	(60)
Settlements	0	1
Benefit obligation-end of fiscal year	897	990	839
Accumulated benefit obligation	892	982
Change in Plan Assets:
Fair value of plan assets-beginning of fiscal year	973	783
Actual return on plan assets	126	166
Company contribution	0	84
Benefit payments	(44)	(60)
Fair value of plan assets-end of fiscal year	1,055	973	783
Funded status at end of fiscal year	158	(17)
Recognized in Consolidated Balance Sheets:
Noncurrent asset	(192)	(23)
Current liability	(8)	(8)
Noncurrent liability	(26)	(32)
Funded status at end of fiscal year	158	(17)
Other Postretirement Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation-beginning of fiscal year	32	38
Service cost	0	0	0
Interest cost	1	1	1
Actuarial (gain) loss	(4)	(3)
Benefit payments	(4)	(4)
Settlements	0	0
Benefit obligation-end of fiscal year	25	32	38
Change in Plan Assets:
Fair value of plan assets-beginning of fiscal year	0	0
Actual return on plan assets	0	0
Company contribution	4	4
Benefit payments	(4)	(4)
Fair value of plan assets-end of fiscal year	0	0	0
Funded status at end of fiscal year	(25)	(32)
Recognized in Consolidated Balance Sheets:
Noncurrent asset	0	0
Current liability	(4)	(4)
Noncurrent liability	(21)	(28)
Funded status at end of fiscal year	$ (25)	$ (32)