Business Restructuring Charges - Summary of Restructuring Accrual Activity (Detail) - USD ($) $ in Millions	1 Months Ended	6 Months Ended
	Dec. 31, 2015	Mar. 31, 2016
Restructuring Reserve [Roll Forward]
Balance at September 30, 2015		$ 62
Charged to expense		149
Cash payments		(84)
Non-cash settlements		(25)
Other adjustments		(59)
Balance at March 31, 2016		43
Write-off of assets relating to the sale of a business	$ 28
Employee Termination
Restructuring Reserve [Roll Forward]
Balance at September 30, 2015		62
Charged to expense		33
Cash payments		(52)
Non-cash settlements		0
Other adjustments		0
Balance at March 31, 2016		43
Share-based Compensation
Restructuring Reserve [Roll Forward]
Balance at September 30, 2015		0
Charged to expense		25
Cash payments		0
Non-cash settlements		(25)
Other adjustments		0
Balance at March 31, 2016		0
Other
Restructuring Reserve [Roll Forward]
Balance at September 30, 2015		0
Charged to expense		91
Cash payments		(32)
Non-cash settlements		0
Other adjustments		(59)
Balance at March 31, 2016		$ 0