Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
AOCI Attributable to Parent, Net of Tax
Balance, beginning of year	$ 4,394	$ 6,074
Other comprehensive income (loss) before reclassification adjustments	35	153	$ (249)
Amounts reclassified from AOCI	(32)	(29)	9
Other comprehensive income (loss)	3	124	(240)
Balance, ending of year	4,354	4,394	6,074
Total
AOCI Attributable to Parent, Net of Tax
Balance, beginning of year	(256)	(380)	(140)
Balance, ending of year	(253)	(256)	(380)
Postretirement Benefit Plans
AOCI Attributable to Parent, Net of Tax
Balance, beginning of year	17	14	(17)
Other comprehensive income (loss) before reclassification adjustments	(7)	5	28
Amounts reclassified from AOCI	0	(2)	3
Other comprehensive income (loss)	(7)	3	31
Balance, ending of year	10	17	14
Derivative Instruments
AOCI Attributable to Parent, Net of Tax
Balance, beginning of year	26	37	(33)
Other comprehensive income (loss) before reclassification adjustments	(14)	16	64
Amounts reclassified from AOCI	(35)	(27)	6
Other comprehensive income (loss)	(49)	(11)	70
Balance, ending of year	(23)	26	37
Foreign Currency
AOCI Attributable to Parent, Net of Tax
Balance, beginning of year	(299)	(431)	(90)
Other comprehensive income (loss) before reclassification adjustments	56	132	(341)
Amounts reclassified from AOCI	3	0	0
Other comprehensive income (loss)	59	132	(341)
Balance, ending of year	$ (240)	$ (299)	$ (431)