Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	$ 4,354
Other comprehensive income (loss) before reclassification adjustments	(57)	$ 34
Amounts reclassified from AOCI	(3)	(10)
Other comprehensive income (loss)	(60)	24
Balance, end of period	4,588	4,432
Total
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(253)	(256)
Balance, end of period	(313)	(232)
Postretirement Benefit Plans
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	10	17
Other comprehensive income (loss) before reclassification adjustments	0	0
Amounts reclassified from AOCI	(1)	0
Other comprehensive income (loss)	(1)	0
Balance, end of period	9	17
Derivative Instruments
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(23)	26
Other comprehensive income (loss) before reclassification adjustments	15	(15)
Amounts reclassified from AOCI	(2)	(10)
Other comprehensive income (loss)	13	(25)
Balance, end of period	(10)	1
Foreign Currency
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(240)	(299)
Other comprehensive income (loss) before reclassification adjustments	(72)	49
Amounts reclassified from AOCI	0	0
Other comprehensive income (loss)	(72)	49
Balance, end of period	$ (312)	$ (250)