Income Taxes Temporary Differences And Carryforwards in Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Deferred Tax Expense from Stock Options Exercised	$ 180
Deferred tax assets
Accrued expenses and reserves	891	$ 1,175
Employee and retiree benefits	13	438
Net operating loss and other credit carryforwards	5,490	4,483
Research and development	188	85
Joint ventures and partnerships	0	49
Deferred Tax Assets, Other	26	19
Gross deferred tax assets	6,608	6,249
Valuation allowances	(3,838)	(3,400)
Net deferred tax assets	2,770	2,849
Net deferred tax asset	627	925
Deferred tax liabilities
Property, plant and equipment	247	87
Joint ventures and partnerships	789	0
Intangible assets	1,107	1,837
Net deferred tax liabilities	$ 2,143	$ 1,924