Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Sep. 30, 2023
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, beginning balance	$ 26,598
Stockholders' equity, ending balance	26,555	$ 16,714
Accumulated other comprehensive income (loss)	(1,090)	(1,255)	$ (1,253)
Foreign currency translation, tax	13	28
Amortization of deferred actuarial losses, tax	2	4
Gains deferred during the period, tax	(2)	(3)
Reclassification of (gains) losses to sales and cost of sales, tax	0	0
Accumulated other comprehensive income (loss)
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, beginning balance	(1,253)	(1,485)
Stockholders' equity, ending balance	(1,090)	(1,255)
Foreign currency translation
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, beginning balance	(1,012)	(1,265)
Other comprehensive income (loss), net of tax of $28 and $13, respectively	172	236
Stockholders' equity, ending balance	(840)	(1,029)
Pension and postretirement
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, beginning balance	(247)	(222)
Amortization of deferred actuarial losses into earnings, net of tax of $4 and $2, respectively	(12)	(16)
Stockholders' equity, ending balance	(259)	(238)
Cash flow hedges
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, beginning balance	6	2
Gains deferred during the period, net of taxes of $(3) and $(2), respectively	6	9
Reclassification of realized (gains) losses to sales and cost of sales, net of tax of $— and $—, respectively	(3)	1
Stockholders' equity, ending balance	$ 9	$ 12