Valuation and Qualifying Accounts Schedule II (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Accounts Receivable - Allowance for Doubtful Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	$ 173	$ 169	$ 172
Provision charged to costs and expenses	20	37	14
Accounts charged off, net of recoveries	(21)	(21)	(17)
Acquisition (divestiture) of businesses	0	(10)	0
Currency translation	1	(2)	0
Balance at end of period	173	173	169
Deferred Tax Assets - Valuation Allowance
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	5,068	5,088	3,735
Allowance provision for new operating and other loss carryforwards	624	195	1,639
Allowance provision (benefits)	(174)	(215)	(286)
Balance at end of period	$ 5,518	$ 5,068	$ 5,088