Income Taxes Temporary Differences And Carryforwards in Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Deferred tax assets
Accrued expenses and reserves	$ 490	$ 891
Employee and retiree benefits	193	373
Net operating loss and other credit carryforwards	6,510	5,130
Research and development	93	188
Other, net	0	26
Gross deferred tax assets	7,286	6,608
Valuation allowances	(5,195)	(3,838)
Net deferred tax assets	2,091	2,770
Deferred tax liabilities
Property, plant and equipment	172	247
Joint ventures and partnerships	306	789
Intangible assets	713	1,107
Other, net	72	0
Net deferred tax liabilities	1,263	2,143
Net deferred tax asset	828	$ 627
Deferred Tax Expense from Stock Options Exercised	$ 179