Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, Beginning balance	$ 8,447	$ 8,273
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Stockholders' equity, Ending balance	9,923	8,447	$ 8,273
Accumulated other comprehensive income (loss)	(872)	(1,577)	(1,722)
Accumulated other comprehensive income (loss)
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, Beginning balance	(1,577)	(1,722)	(1,015)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Stockholders' equity, Ending balance	(872)	(1,577)	(1,722)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, Beginning balance	(711)	(794)	(600)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Other comprehensive income (loss), net of taxes of $(5), $29 and $(16), respectively	82	83	(194)
Stockholders' equity, Ending balance	(629)	(711)	(794)
Cash flow hedges
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, Beginning balance	(2)	0	5
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Gains (Losses) deferred during the period, net of taxes of $(15), $2 and $1, respectively	51	(9)	(3)
Reclassifications of realized (gains) losses to sales and cost of sales, net of taxes of $11, $(2) and $0 respectively	(33)	7	(2)
Stockholders' equity, Ending balance	16	(2)	0
Pension and postretirement
Accumulated other comprehensive income [Roll Forward]
Stockholders' equity, Beginning balance	(864)	(928)	(420)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Actuarial gains (losses) deferred during the period, net of taxes of $(150), $15, and $165, respectively	499	(49)	(560)
Amortization of deferred actuarial losses into earnings, net of taxes of $(34), $(34) and $(15), respectively	106	113	52
Stockholders' equity, Ending balance	$ (259)	$ (864)	$ (928)