Income Taxes - Reconciliation Using U.S. Statutory Rate (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Computed tax expense at the federal statutory rate	$ 101	$ 68	$ (132)
Impact of taxation at different rates, repatriation, losses and other	(75)	(37)	(24)
Impact of increase (decrease) in valuation allowance on deferred taxes	(7)	7	(7)
Impact of foreign losses for which a current tax benefit is not available	1		9
Impact of non-deductible net currency losses		2	(1)
U.S. and state benefits from research and experimentation activities	(2)	(2)	(2)
Provision (settlement) of unrecognized tax benefits	7	1	(7)
Benefit from prior currency loss		(3)
Impact of goodwill impairment charge			123
Permanent differences, net	5
State taxes, net of federal effect	(1)	(2)	(4)
Provision (benefit) for income taxes	$ 29	$ 34	$ (45)