Accumulated Other Comprehensive Loss - Schedule of Changes in Accumulated Other Comprehensive Loss by Component (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 3,576	$ 3,605	$ 3,711	$ 3,675
Other comprehensive income (loss) before reclassifications	(34)	89	(26)	22
Amounts reclassified from accumulated other comprehensive loss	4	7	14	13
Other comprehensive income (loss)	(30)	96	(12)	35
Balance at end of period	3,496	3,628	3,496	3,628
Total accumulated other comprehensive loss, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(639)	(833)	(657)	(772)
Balance at end of period	(669)	(737)	(669)	(737)
Pension and other postretirement benefit plan adjustments, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(328)	(420)	(335)	(431)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive loss	3	6	10	17
Other comprehensive income (loss)	3	6	10	17
Balance at end of period	(325)	(414)	(325)	(414)
Accumulated currency translation adjustments, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(278)	(382)	(281)	(296)
Other comprehensive income (loss) before reclassifications	(39)	105	(36)	19
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Other comprehensive income (loss)	(39)	105	(36)	19
Balance at end of period	(317)	(277)	(317)	(277)
Net unrealized losses on cash flow hedges, net of tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(33)	(31)	(41)	(45)
Other comprehensive income (loss) before reclassifications	5	(16)	10	3
Amounts reclassified from accumulated other comprehensive loss	1	1	4	(4)
Other comprehensive income (loss)	6	(15)	14	(1)
Balance at end of period	$ (27)	$ (46)	$ (27)	$ (46)