AVAILABLE-FOR-SALE SECURITIES, Contractual Maturities (Details) - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023
Fair value
Total	$ 8,260	$ 9,181
Bank
Amortized cost
Within one year	803
After one but within five years	1,592
After five but within ten years	2,172
After ten years	4,339
Cost basis	8,906	10,433
Fair value
Within one year	798
After one but within five years	1,531
After five but within ten years	2,001
After ten years	3,930
Total	$ 8,260	9,181
Weighted-average yield
Within one year	3.36%
After one but within five years	2.61%
After five but within ten years	1.33%
After ten years	2.30%
Total	2.21%
Bank | Agency residential MBS
Amortized cost
Within one year	$ 1
After one but within five years	87
After five but within ten years	1,696
After ten years	2,363
Cost basis	4,147	4,865
Fair value
Within one year	1
After one but within five years	85
After five but within ten years	1,583
After ten years	2,154
Total	$ 3,823	4,211
Weighted-average yield
Within one year	2.08%
After one but within five years	2.53%
After five but within ten years	1.29%
After ten years	2.05%
Total	1.75%
Bank | Agency commercial MBS
Amortized cost
Within one year	$ 71
After one but within five years	908
After five but within ten years	387
After ten years	49
Cost basis	1,415	1,464
Fair value
Within one year	70
After one but within five years	854
After five but within ten years	332
After ten years	40
Total	$ 1,296	1,253
Weighted-average yield
Within one year	2.85%
After one but within five years	1.48%
After five but within ten years	1.18%
After ten years	1.87%
Total	1.48%
Bank | Agency CMOs
Amortized cost
Within one year	$ 0
After one but within five years	4
After five but within ten years	34
After ten years	1,356
Cost basis	1,394	1,448
Fair value
Within one year	0
After one but within five years	4
After five but within ten years	31
After ten years	1,190
Total	$ 1,225	1,183
Weighted-average yield
Within one year	0.00%
After one but within five years	2.27%
After five but within ten years	1.51%
After ten years	1.86%
Total	1.85%
Bank | U.S. Treasuries
Amortized cost
Within one year	$ 467
After one but within five years	239
After five but within ten years	0
After ten years	0
Cost basis	706	1,261
Fair value
Within one year	466
After one but within five years	238
After five but within ten years	0
After ten years	0
Total	$ 704	1,240
Weighted-average yield
Within one year	3.81%
After one but within five years	4.61%
After five but within ten years	0.00%
After ten years	0.00%
Total	4.08%
Bank | Other agency obligations
Amortized cost
Within one year	$ 257
After one but within five years	272
After five but within ten years	28
After ten years	8
Cost basis	565	710
Fair value
Within one year	254
After one but within five years	269
After five but within ten years	27
After ten years	9
Total	$ 559	679
Weighted-average yield
Within one year	2.70%
After one but within five years	3.70%
After five but within ten years	2.42%
After ten years	3.07%
Total	3.17%
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	553
Cost basis	553	527
Fair value
Within one year	0
After one but within five years	0
After five but within ten years	0
After ten years	527
Total	$ 527	463
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	4.35%
Total	4.35%
Bank | Corporate bonds
Amortized cost
Within one year	$ 7
After one but within five years	77
After five but within ten years	23
After ten years	0
Cost basis	107	140
Fair value
Within one year	7
After one but within five years	76
After five but within ten years	23
After ten years	0
Total	$ 106	134
Weighted-average yield
Within one year	3.48%
After one but within five years	5.71%
After five but within ten years	5.02%
After ten years	0.00%
Total	5.41%
Bank | Other
Amortized cost
Within one year	$ 0
After one but within five years	5
After five but within ten years	4
After ten years	10
Cost basis	19	18
Fair value
Within one year	0
After one but within five years	5
After five but within ten years	5
After ten years	10
Total	$ 20	$ 18
Weighted-average yield
Within one year	0.00%
After one but within five years	7.29%
After five but within ten years	2.68%
After ten years	7.72%
Total	6.36%