SEC Schedule, Article 12-09, Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
SEC Schedule, 12-09, valuation allowances and reserves, amount, beginning balance	$ 846	$ 223	$ 267
Provision during period	488	669	23
Allowance adjustments	(30)	(46)	(67)
SEC Schedule, 12-09, valuation allowances and reserves, amount, ending balance	1,304	846	223
SEC Schedule, 12-09, Allowance, Doubtful Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
SEC Schedule, 12-09, valuation allowances and reserves, amount, beginning balance	15	20	21
Provision during period	15	12	13
Allowance adjustments	(16)	(17)	(14)
SEC Schedule, 12-09, valuation allowances and reserves, amount, ending balance	$ 14	$ 15	$ 20