Income Taxes - Provision for Income Taxes from Continuing Operations (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Federal	$ (50)	$ 235	$ 665
State and local, including Puerto Rico	47	41	73
Foreign	400	300	387
Total, Current	397	576	1,124
Domestic	(184)	(577)	(201)
Foreign	(101)	(56)	(61)
Total, Deferred	(286)	(633)	(262)
Income tax provision	$ 111	$ (57)	$ 862