Income Taxes Temporary Differences And Carryforwards in Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Deferred tax assets
Accrued expenses and reserves	$ 474	$ 437
Employee and retiree benefits	286	265
Deferred Tax Assets, Property, Plant and Equipment	182	0
Net operating loss and other credit carryforwards	6,306	5,664
Research and development	112	106
Other, net	99	0
Gross deferred tax assets	7,459	6,472
Valuation allowances	(5,518)	(5,068)
Net deferred tax assets	1,941	1,404
Deferred tax liabilities
Property, plant and equipment	0	139
Joint ventures and partnerships	730	499
Intangible assets	734	759
Other, net	0	43
Deferred Tax Liabilities, Gross	1,464	1,440
Deferred Income Tax Liabilities, Net		$ (36)
Deferred Tax Assets (Liabilities), Net	477
Operating Loss Carryforwards	25,000
Net Operating Loss Carry Forwards That Will Expire	15,100
Tax Credit Carryforward, Amount	$ 35