Business Restructuring Charges - Summary of Restructuring Accrual Activity (Detail) $ in Millions	9 Months Ended
	Jun. 30, 2017 USD ($)
Restructuring Reserve [Roll Forward]
Balance at September 30, 2016	$ 69
Charged to expense	54
Cash payments	(56)
Non-cash settlements	(9)
Other adjustments	7
Balance at June 30, 2017	51
Employee Termination
Restructuring Reserve [Roll Forward]
Balance at September 30, 2016	67
Charged to expense	3
Cash payments	(22)
Non-cash settlements	0
Other adjustments	0
Balance at June 30, 2017	48
Other
Restructuring Reserve [Roll Forward]
Balance at September 30, 2016	2
Charged to expense	51
Cash payments	(34)
Non-cash settlements	(9)
Other adjustments	7
Balance at June 30, 2017	$ 3