Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, beginning balance	$ 16,316	$ 9,923
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Stockholders' equity, ending balance	26,598	16,316	$ 9,923
Accumulated other comprehensive income (loss)	(1,253)	(1,485)	(872)
Foreign currency translation, tax	26	(62)	(5)
Actuarial gains (losses) deferred during the period, tax expense (benefit)	0	(10)	150
Amortization of deferred actuarial losses into earnings, tax benefit	(17)	21	34
Gains deferred during the period, tax expense	11	6	15
Reclassification of (gains) losses to sales and cost of sales, tax	4	10	11
Accumulated other comprehensive income (loss)
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, beginning balance	(1,485)	(872)	(1,577)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Stockholders' equity, ending balance	(1,253)	(1,485)	(872)
Foreign currency translation
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, beginning balance	(1,265)	(629)	(711)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Other comprehensive income (loss), net of tax of $(5), $(62) and $26, respectively	158	(636)	82
Reclassified to gain on sale of business	95	0	0
Stockholders' equity, ending balance	(1,012)	(1,265)	(629)
Pension and postretirement
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, beginning balance	(222)	(259)	(864)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Reclassified to gain on sale of business	22	0	0
Actuarial gains (losses) deferred during the period, net of taxes of $(150), $10 and $0, respectively	4	(33)	499
Amortization of deferred actuarial losses into earnings, net of tax of $(34), $(21) and $17, respectively	(51)	70	106
Stockholders' equity, ending balance	(247)	(222)	(259)
Cash flow hedges
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, beginning balance	2	16	(2)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Reclassified to gain on sale of business	(19)	0	0
Gains deferred during the period, net of taxes of $(15), $(6) and $(11), respectively	37	18	51
Reclassifications of realized (gains) losses to sales and cost of sales, net of tax of $11, $10 and $4, respectively	(14)	(32)	(33)
Stockholders' equity, ending balance	$ 6	$ 2	$ 16