FAIR VALUE, Level 3 Financial Assets and Liabilities, Roll Forward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Sep. 30, 2022
Percentage of instruments measured at fair value on a recurring basis
Instruments measured at fair value, percentage of assets (in hundredths)	15.00%		15.00%		14.00%
Instruments measured at fair value, percentage of liabilities (in hundredths)	2.00%		2.00%		2.00%
Instruments measured at fair value, level 3, percentage of assets (in hundredths)	1.00%		1.00%		1.00%
Trading liabilities | Other
Changes in Level 3 recurring fair value measurements, liabilities [Roll Forward]
Fair value beginning of period		$ (1)
Total gains/(losses) included in earnings		1
Purchases and contributions		0
Sales and distributions		0
Transfers:
Into Level 3		0
Out of Level 3		0
Fair value end of period		0		$ 0
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period		0
Derivative liabilities | Other
Changes in Level 3 recurring fair value measurements, liabilities [Roll Forward]
Fair value beginning of period	$ (4)	0	$ (3)	(1)
Total gains/(losses) included in earnings	0	(1)	(1)	0
Purchases and contributions	0	0	0	0
Sales and distributions	0	0	0	0
Transfers:
Into Level 3	0	0	0	0
Out of Level 3	0	0	0	0
Fair value end of period	(4)	(1)	(4)	(1)
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	0	(1)	(1)	(1)
Trading assets | Trading assets
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of period	3	13	1	14
Total gains/(losses) included in earnings	(1)	(1)	(1)	1
Purchases and contributions	19	37	55	91
Sales and distributions	(12)	(49)	(46)	(106)
Transfers:
Into Level 3	0	0	0	0
Out of Level 3	0	0	0	0
Fair value end of period	9	0	9	0
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	1	0	1	0
Derivative assets
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of period		0		0
Total gains/(losses) included in earnings		2		2
Purchases and contributions		0		0
Sales and distributions		0		0
Transfers:
Into Level 3		0		0
Out of Level 3		0		0
Fair value end of period		2		2
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period		2		2
Other investments | All other
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of period	28	53	29	98
Total gains/(losses) included in earnings	1	0	0	0
Purchases and contributions	0	0	0	7
Sales and distributions	0	(2)	0	(42)
Transfers:
Into Level 3	0	0	0	0
Out of Level 3	0	0	0	(12)
Fair value end of period	29	51	29	51
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	$ 1	$ 5	$ 0	$ 5