Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2020
Accumulated other comprehensive income [Roll Forward]
Beginning balance			$ 8,447
Ending balance	$ 9,180	$ 7,563	9,180	$ 7,563
Accumulated other comprehensive income (loss)	(1,322)	(1,903)	(1,322)	(1,903)	$ (1,577)
Foreign currency translation [Member]
Accumulated other comprehensive income [Roll Forward]
Beginning balance	(522)	(695)	(711)	(794)
Other comprehensive income (loss), foreign currency translation, net of tax of $(13), $(13), $6 and $(7), respectively	(20)	(282)	169	(183)
Ending balance	(542)	(977)	(542)	(977)
Pension and post retirement [Member]
Accumulated other comprehensive income [Roll Forward]
Beginning balance	(837)	(900)	(864)	(928)
Amortization of deferred actuarial losses into earnings, net of tax of $(8), $(8), $(16) and $(17), respectively	27	30	54	58
Ending balance	(810)	(870)	(810)	(870)
Cash Flow Hedges [Member]
Accumulated other comprehensive income [Roll Forward]
Beginning balance	29	19	(2)	0
Deferral of gains (losses) arising during the period, net of tax of $(2), $23, $(13) and $17, respectively	9	(74)	43	(53)
Reclassification of realized gains (losses) to sales and cost of sales, net of tax of $3, $1, $4 and $1, respectively	(8)	(1)	(11)	(3)
Ending balance	$ 30	$ (56)	$ 30	$ (56)