FAIR VALUE, Level 3 Financial Assets and Liabilities, Roll Forward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Sep. 30, 2021
Percentage of instruments measured at fair value on a recurring basis
Instruments measured at fair value, percentage of assets (in hundredths)	16.00%		16.00%		19.00%
Instruments measured at fair value, percentage of liabilities (in hundredths)	1.00%		1.00%		1.00%
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)	$ (1)	$ 0	$ 0
Total gains/(losses) included in earnings	1	1	0	0
Purchases and contributions	0	0	0	0
Sales, distributions, and deconsolidations	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	0	0	0	0
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	0	0	0	0
Derivative liabilities | Other
Changes in Level 3 recurring fair value measurements, liabilities [Roll Forward]
Fair value beginning of period	0	(4)	(1)	(5)
Total gains/(losses) included in earnings	(1)	0	0	1
Purchases and contributions	0	0	0	0
Sales, distributions, and deconsolidations	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	(1)	(4)	(1)	(4)
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	(1)	0	(1)	1
Trading assets | Trading assets
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of period	13	5	14	12
Total gains/(losses) included in earnings	(1)	0	1	0
Purchases and contributions	37	10	91	26
Sales, distributions, and deconsolidations	(49)	(5)	(106)	(28)
Transfers:
Into Level 3	0	0	0	0
Out of Level 3	0	0	0	0
Fair value end of period	0	10	0	10
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	0	0	0	0
Derivative assets | Other
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of period	0	0	0	0
Total gains/(losses) included in earnings	2	1	2	1
Purchases and contributions	0	0	0	0
Sales, distributions, and deconsolidations	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	2	1	2	1
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	2	1	2	1
Other investments | Private equity investments
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of period	23	52	75	37
Total gains/(losses) included in earnings	4	14	4	29
Purchases and contributions	0	0	0	0
Sales, distributions, and deconsolidations	0	0	(40)	0
Transfers:
Into Level 3	0	0	0	0
Out of Level 3	0	0	(12)	0
Fair value end of period	27	66	27	66
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	4	14	4	29
Other investments | All other
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of period	30	23	23	22
Total gains/(losses) included in earnings	(4)	0	(4)	1
Purchases and contributions	0	0	7	0
Sales, distributions, and deconsolidations	(2)	0	(2)	0
Transfers:
Into Level 3	0	0	0	0
Out of Level 3	0	0	0	0
Fair value end of period	24	23	24	23
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	$ 1	$ 0	$ 1	$ 0