Valuation and Qualifying Accounts Schedule II (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
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		$ 173	$ 70	$ 64
Provision charged to costs and expenses		39	45	27
Reserve adjustments		(9)	(8)	(5)
Accounts charged off		(41)	(25)	(16)
Acquisition of businesses		18	91	1
Currency translation		2	0	(1)
Balance at end of period	173	182	173	70
Deferred Tax Assets - Valuation Allowance
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period		3,400	1,151	1,111
Acquisition of businesses		53	2,459	0
Allowance provision for new operating and other loss carryforwards		542	121	23
Allowance provision benefits		(157)	(331)	17
Balance at end of period	$ 3,400	$ 3,838	$ 3,400	$ 1,151