AVAILABLE-FOR-SALE SECURITIES, Contractual Maturities (Details) - USD ($) $ in Millions	Jun. 30, 2022	Sep. 30, 2021
Carrying value
Total	$ 10,464	$ 8,315
Weighted-average yield
Within one year (in hundredths)	2.15%
After one but within five years (in hundredths)	2.23%
After five but within ten years (in hundredths)	1.33%
After ten years (in hundredths)	1.89%
Total (in hundredths)	1.76%
Bank
Amortized cost
Within one year	$ 20
After one but within five years	2,089
After five but within ten years	3,673
After ten years	5,407
Cost basis	11,189	8,322
Carrying value
Within one year	20
After one but within five years	2,039
After five but within ten years	3,410
After ten years	4,995
Total	10,464	8,315
Bank | Agency residential MBS
Amortized cost
Within one year	0
After one but within five years	135
After five but within ten years	2,621
After ten years	3,147
Cost basis	5,903	5,168
Carrying value
Within one year	0
After one but within five years	133
After five but within ten years	2,468
After ten years	2,912
Total	5,513	5,189
Bank | Agency commercial MBS
Amortized cost
Within one year	19
After one but within five years	481
After five but within ten years	853
After ten years	75
Cost basis	1,428	1,285
Carrying value
Within one year	19
After one but within five years	452
After five but within ten years	746
After ten years	67
Total	1,284	1,264
Bank | Agency CMOs
Amortized cost
Within one year	0
After one but within five years	8
After five but within ten years	34
After ten years	1,664
Cost basis	1,706	1,854
Carrying value
Within one year	0
After one but within five years	8
After five but within ten years	32
After ten years	1,506
Total	1,546	1,847
Bank | Other agency obligations
Amortized cost
Within one year	0
After one but within five years	467
After five but within ten years	99
After ten years	12
Cost basis	578
Carrying value
Within one year	0
After one but within five years	456
After five but within ten years	98
After ten years	13
Total	567
Bank | Non-agency residential MBS
Amortized cost
Within one year	0
After one but within five years	0
After five but within ten years	0
After ten years	496
Cost basis	496
Carrying value
Within one year	0
After one but within five years	0
After five but within ten years	0
After ten years	485
Total	485
Bank | U.S. Treasuries
Amortized cost
Within one year	0
After one but within five years	915
After five but within ten years	4
After ten years	0
Cost basis	919	15
Carrying value
Within one year	0
After one but within five years	909
After five but within ten years	3
After ten years	0
Total	912	$ 15
Bank | Corporate bonds
Amortized cost
Within one year	0
After one but within five years	78
After five but within ten years	62
After ten years	0
Cost basis	140
Carrying value
Within one year	0
After one but within five years	77
After five but within ten years	63
After ten years	0
Total	140
Bank | Other
Amortized cost
Within one year	1
After one but within five years	5
After five but within ten years	0
After ten years	13
Cost basis	19
Carrying value
Within one year	1
After one but within five years	4
After five but within ten years	0
After ten years	12
Total	$ 17