Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period			$ 4,394
Other comprehensive (loss) income before reclassification adjustments	$ (12)	$ (5)	22	$ 149
Amounts reclassified from AOCI	(10)	(5)	(20)	(10)
Other comprehensive (loss) income	(22)	(10)	2	139
Balance, end of period	4,831	5,214	4,831	5,214
Total
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(232)	(231)	(256)	(380)
Balance, end of period	(254)	(241)	(254)	(241)
Postretirement Benefit Plans
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	17	14	17	14
Other comprehensive (loss) income before reclassification adjustments	0	0	0	0
Amounts reclassified from AOCI	(1)	0	(1)	0
Other comprehensive (loss) income	(1)	0	(1)	0
Balance, end of period	16	14	16	14
Derivative Instruments
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	1	35	26	37
Other comprehensive (loss) income before reclassification adjustments	12	(15)	(3)	(12)
Amounts reclassified from AOCI	(9)	(5)	(19)	(10)
Other comprehensive (loss) income	3	(20)	(22)	(22)
Balance, end of period	4	15	4	15
Foreign Currency
AOCI Attributable to Parent, Net of Tax
Balance, beginning of period	(250)	(280)	(299)	(431)
Other comprehensive (loss) income before reclassification adjustments	(24)	10	25	161
Amounts reclassified from AOCI	0	0	0	0
Other comprehensive (loss) income	(24)	10	25	161
Balance, end of period	$ (274)	$ (270)	$ (274)	$ (270)