Valuation and Qualifying Accounts Schedule II (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Movement in Valuation Allowances and Reserves [Roll Forward]
Acquisition of businesses	$ 2,400
Accounts Receivable - Allowance for Doubtful Accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period		$ 182	$ 173	$ 70
Provision charged to costs and expenses		40	39	45
Reserve adjustments		(24)	(9)	(8)
Accounts charged off		(21)	(41)	(25)
Acquisition of businesses		0	18	91
Currency translation		0	2	0
Balance at end of period	173	177	182	173
Deferred Tax Assets - Valuation Allowance
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period		3,838	3,400	1,151
Acquisition of businesses		0	53	2,459
Allowance provision for new operating and other loss carryforwards		1,665	542	121
Allowance provision benefits		(308)	(157)	(331)
Balance at end of period	$ 3,400	$ 5,195	$ 3,838	$ 3,400