Benefit Plans - Changes in Fair Value of Foreign Pension Assets Measured Using Level 3 Inputs (Detail) - Foreign Plans - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning fair value	$ 575
Ending fair value	624	$ 575
Insurance contracts
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning fair value	90
Ending fair value	102	90
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning fair value	90
Ending fair value	102	90
Significant Unobservable Inputs (Level 3) | Insurance contracts
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning fair value	90	78
Return on assets	8	4
Purchases, sales and settlements, net	2	16
Transfers in from other categories		1
Exchange rate changes	1	(9)
Ending fair value	$ 102	$ 90