ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS), AOCI Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year	$ 7,176	$ 6,643
OCI before reclassifications and taxes	(96)	45	$ 24
Amounts reclassified from AOCI, before tax	10	2	(5)
Pre-tax net OCI	(86)	47	19
Income tax effect	34	(13)	(11)
Total other comprehensive income/(loss), net of tax	(52)	34	8
Balance, end of year	8,303	7,176	6,643
Net investment hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year	115	110	88
OCI before reclassifications and taxes	(44)	7	29
Amounts reclassified from AOCI, before tax	0	0	0
Pre-tax net OCI	(44)	7	29
Income tax effect	10	(2)	(7)
Total other comprehensive income/(loss), net of tax	(34)	5	22
Balance, end of year	81	115	110
Net investment hedges | Cumulative adjustments for changes in accounting principles
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year			0
Currency translations
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year	(140)	(135)	(111)
OCI before reclassifications and taxes	48	(5)	(24)
Amounts reclassified from AOCI, before tax	2	0	0
Pre-tax net OCI	50	(5)	(24)
Income tax effect	0	0	0
Total other comprehensive income/(loss), net of tax	50	(5)	(24)
Balance, end of year	(90)	(140)	(135)
Currency translations | Cumulative adjustments for changes in accounting principles
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year			0
Subtotal: net investment hedges and currency translations
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year	(25)	(25)	(23)
OCI before reclassifications and taxes	4	2	5
Amounts reclassified from AOCI, before tax	2	0	0
Pre-tax net OCI	6	2	5
Income tax effect	10	(2)	(7)
Total other comprehensive income/(loss), net of tax	16	0	(2)
Balance, end of year	(9)	(25)	(25)
Subtotal: net investment hedges and currency translations | Cumulative adjustments for changes in accounting principles
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year			0
Available-for-sale securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year	89	21	(46)
OCI before reclassifications and taxes	(119)	94	98
Amounts reclassified from AOCI, before tax	(7)	(3)	0
Pre-tax net OCI	(126)	91	98
Income tax effect	32	(23)	(27)
Total other comprehensive income/(loss), net of tax	(94)	68	71
Balance, end of year	(5)	89	21
Available-for-sale securities | Cumulative adjustments for changes in accounting principles
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year			(4)
Cash flow hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year	(53)	(19)	42
OCI before reclassifications and taxes	19	(51)	(79)
Amounts reclassified from AOCI, before tax	15	5	(5)
Pre-tax net OCI	34	(46)	(84)
Income tax effect	(8)	12	23
Total other comprehensive income/(loss), net of tax	26	(34)	(61)
Balance, end of year	(27)	(53)	(19)
Cash flow hedges | Cumulative adjustments for changes in accounting principles
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year			0
Accumulated other comprehensive (loss) income
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year	11	(23)	(27)
Total other comprehensive income/(loss), net of tax	(52)	34	8
Balance, end of year	$ (41)	$ 11	(23)
Accumulated other comprehensive (loss) income | Cumulative adjustments for changes in accounting principles
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning of year			$ (4)