AVAILABLE-FOR-SALE SECURITIES, Contractual Maturities (Details) - USD ($) $ in Millions	Sep. 30, 2022	Sep. 30, 2021
Carrying value
Total	$ 9,885	$ 8,315
Bank
Amortized cost
Within one year	21
After one but within five years	2,454
After five but within ten years	3,441
After ten years	5,184
Cost basis	11,100	8,322
Carrying value
Within one year	21
After one but within five years	2,324
After five but within ten years	3,026
After ten years	4,514
Total	$ 9,885	8,315
Weighted-average yield
Within one year	1.91%
After one but within five years	2.31%
After five but within ten years	1.39%
After ten years	1.91%
Total	1.84%
Bank | Agency residential MBS
Amortized cost
Within one year	$ 0
After one but within five years	147
After five but within ten years	2,516
After ten years	2,999
Cost basis	5,662	5,168
Carrying value
Within one year	0
After one but within five years	140
After five but within ten years	2,242
After ten years	2,612
Total	$ 4,994	5,189
Weighted-average yield
Within one year	0.00%
After one but within five years	2.45%
After five but within ten years	1.25%
After ten years	1.76%
Total	1.55%
Bank | Agency commercial MBS
Amortized cost
Within one year	$ 15
After one but within five years	714
After five but within ten years	716
After ten years	73
Cost basis	1,518	1,285
Carrying value
Within one year	15
After one but within five years	644
After five but within ten years	588
After ten years	63
Total	$ 1,310	1,264
Weighted-average yield
Within one year	1.91%
After one but within five years	1.70%
After five but within ten years	1.22%
After ten years	1.69%
Total	1.47%
Bank | Agency CMOs
Amortized cost
Within one year	$ 0
After one but within five years	12
After five but within ten years	30
After ten years	1,595
Cost basis	1,637	1,854
Carrying value
Within one year	0
After one but within five years	12
After five but within ten years	27
After ten years	1,365
Total	$ 1,404	1,847
Weighted-average yield
Within one year	0.00%
After one but within five years	2.08%
After five but within ten years	1.54%
After ten years	1.48%
Total	1.49%
Bank | Other agency obligations
Amortized cost
Within one year	$ 0
After one but within five years	487
After five but within ten years	114
After ten years	12
Cost basis	613
Carrying value
Within one year	0
After one but within five years	464
After five but within ten years	107
After ten years	11
Total	$ 582
Weighted-average yield
Within one year	0.00%
After one but within five years	2.16%
After five but within ten years	3.55%
After ten years	2.99%
Total	2.43%
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	492
Cost basis	492
Carrying value
Within one year	0
After one but within five years	0
After five but within ten years	0
After ten years	451
Total	$ 451
Weighted-average yield
Within one year	0.00%
After one but within five years	0.00%
After five but within ten years	0.00%
After ten years	4.13%
Total	4.13%
Bank | U.S. Treasuries
Amortized cost
Within one year	$ 6
After one but within five years	1,006
After five but within ten years	2
After ten years	0
Cost basis	1,014	15
Carrying value
Within one year	6
After one but within five years	978
After five but within ten years	2
After ten years	0
Total	$ 986	$ 15
Weighted-average yield
Within one year	1.91%
After one but within five years	2.64%
After five but within ten years	1.30%
After ten years	0.00%
Total	2.63%
Bank | Corporate bonds
Amortized cost
Within one year	$ 0
After one but within five years	83
After five but within ten years	63
After ten years	0
Cost basis	146
Carrying value
Within one year	0
After one but within five years	81
After five but within ten years	60
After ten years	0
Total	$ 141
Weighted-average yield
Within one year	0.00%
After one but within five years	4.12%
After five but within ten years	4.91%
After ten years	0.00%
Total	4.46%
Bank | Other
Amortized cost
Within one year	$ 0
After one but within five years	5
After five but within ten years	0
After ten years	13
Cost basis	18
Carrying value
Within one year	0
After one but within five years	5
After five but within ten years	0
After ten years	12
Total	$ 17
Weighted-average yield
Within one year	0.00%
After one but within five years	4.19%
After five but within ten years	0.00%
After ten years	5.33%
Total	4.95%