FAIR VALUE, Level 3 Financial Assets and Liabilities, Roll Forward (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Sep. 30, 2021
Percentage of instruments measured at fair value on a recurring basis
Instruments measured at fair value, percentage of assets (in hundredths)	28.00%		19.00%
Instruments measured at fair value, percentage of liabilities (in hundredths)	1.00%		1.00%
Instruments measured at fair value, level 3, percentage of assets (in hundredths)	1.00%		1.00%
Derivative liabilities | Other
Changes in Level 3 recurring fair value measurements, liabilities [Roll Forward]
Fair value beginning of period	$ (1)	$ (5)
Total gains included in earnings	1	4
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	0	(1)
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	0	3
Trading assets | Trading assets
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of period	14	12
Total gains included in earnings	2	2
Purchases and contributions	25	6
Sales and distributions	(39)	(17)
Transfers:
Into Level 3	0	0
Out of Level 3	0	0
Fair value end of period	2	3
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	(1)	3
Derivative assets | Other
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of period	0
Total gains 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	1
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	2
Private equity and other investments | Private equity investments
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of period	75	37
Total gains included in earnings	0	15
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	75	52
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	0	15
Private equity and other investments | All other
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of period	23	22
Total gains included in earnings	0	0
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	23	22
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	$ 0	$ 0