Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020
Accumulated other comprehensive income [Roll Forward]
Beginning balance	$ 8,447
Ending balance	8,939	$ 8,459
Accumulated other comprehensive income (loss)	(1,330)	(1,576)	$ (1,577)
Foreign currency translation [Member]
Accumulated other comprehensive income [Roll Forward]
Beginning balance	(711)	(794)
Other comprehensive income (loss), foreign currency translation, net of tax of $19 and $6, respectively	189	99
Ending balance	(522)	(695)
Pension and post retirement [Member]
Accumulated other comprehensive income [Roll Forward]
Beginning balance	(864)	(928)
Amortization of deferred actuarial losses into earnings, net of tax of $(8) and $(9), respectively	27	28
Ending balance	(837)	(900)
Cash Flow Hedges [Member]
Accumulated other comprehensive income [Roll Forward]
Beginning balance	(2)	0
Deferral of gains (losses) arising during the period, net of tax of $(11) and $(6), respectively	34	21
Reclassification of realized gains (losses) to sales and cost of sales, net of tax of $1 and $0, respectively	(3)	(2)
Ending balance	$ 29	$ 19