Income Taxes - Temporary Differences and Carryforwards (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020
Deferred tax assets:
Accrued expenses and reserves	$ 126	$ 115
Employee and retiree benefits	52	53
Net operating loss and other credit carryforwards	1,056	1,072
Property, plant and equipment	159	163
Intangible assets	181	257
Operating lease liabilities	79	80
Foreign currency adjustments	0	17
Research and development	23	20
Other	12	3
Deferred tax assets:	1,688	1,780
Valuation allowances	(1,637)	(1,656)
Deferred tax assets, net	51	124
Deferred tax liabilities:
Unremitted earnings of foreign subsidiaries	32	41
Indirect tax credits	18	0
Operating lease right-of-use assets	79	80
Deferred tax liabilities:	129	121
Net deferred tax asset/(liability)		$ 3
Net deferred tax asset/(liability)	$ (78)