Intangible Assets, Net - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015	Feb. 28, 2017
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Amortization expense related to finite-lived intangible assets	$ 56	$ 50	$ 63
Impairment of indefinite-lived or finite-lived intangible assets	0	0	0
Payments to Acquire Businesses, Net of Cash Acquired	302	9,082	$ 93
Finite-lived Intangible Assets Acquired	$ 104
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	8 years
Goodwill (Note 2 and Note 6)	$ 15,110	$ 15,066		$ 181