Income Taxes - Provision for Income Taxes from Continuing Operations (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Federal	$ 235	$ 665	$ (230)
State and local, including Puerto Rico	41	73	(20)
Foreign	300	387	200
Total, Current	576	1,124	(50)
Domestic	(566)	(201)	(64)
Foreign	(67)	(61)	(10)
Total, Deferred	(633)	(262)	(74)
Income tax provision	$ (57)	$ 862	$ (124)