BANK LOANS, NET, Investment Bank Loan Portfolio by Credit Quality Indicator (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
SBL
Loans by origination fiscal year
Current fiscal year	$ 21	$ 133
Fiscal year before current fiscal year	62	30
Fiscal year two years before current fiscal year	30	15
Fiscal year three years before current fiscal year	20	76
Fiscal year four years before current fiscal year	29	27
Prior	43	52
Revolving loans	19,570	15,900
Total loans held for investment	19,775	16,233
Gross charge-offs
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	0	0
Prior	0	0
Revolving loans	0	0
Gross charge-offs	0	0
SBL | Pass
Loans by origination fiscal year
Current fiscal year	21	131
Fiscal year before current fiscal year	62	30
Fiscal year two years before current fiscal year	30	15
Fiscal year three years before current fiscal year	20	76
Fiscal year four years before current fiscal year	29	27
Prior	43	52
Revolving loans	19,485	15,900
Total loans held for investment	19,690	16,231
SBL | Special mention
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	0	0
Prior	0	0
Revolving loans	85	0
Total loans held for investment	85	0
SBL | Substandard
Loans by origination fiscal year
Current fiscal year	0	2
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	0	0
Prior	0	0
Revolving loans	0	0
Total loans held for investment	0	2
SBL | Doubtful
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	0	0
Prior	0	0
Revolving loans	0	0
Total loans held for investment	0	0
C&I loans
Loans by origination fiscal year
Current fiscal year	746	616
Fiscal year before current fiscal year	744	458
Fiscal year two years before current fiscal year	382	1,179
Fiscal year three years before current fiscal year	1,017	716
Fiscal year four years before current fiscal year	851	686
Prior	3,559	3,318
Revolving loans	3,478	2,980
Total loans held for investment	10,777	9,953
Gross charge-offs
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	0	3
Fiscal year four years before current fiscal year	0	4
Prior	32	38
Revolving loans	1	0
Gross charge-offs	33	45
C&I loans | Pass
Loans by origination fiscal year
Current fiscal year	746	616
Fiscal year before current fiscal year	743	454
Fiscal year two years before current fiscal year	366	1,178
Fiscal year three years before current fiscal year	1,016	716
Fiscal year four years before current fiscal year	849	586
Prior	3,495	3,287
Revolving loans	3,455	2,966
Total loans held for investment	10,670	9,803
C&I loans | Special mention
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	0	4
Fiscal year two years before current fiscal year	16	1
Fiscal year three years before current fiscal year	1	0
Fiscal year four years before current fiscal year	0	54
Prior	0	1
Revolving loans	3	0
Total loans held for investment	20	60
C&I loans | Substandard
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	1	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	2	46
Prior	64	25
Revolving loans	20	12
Total loans held for investment	87	83
C&I loans | Doubtful
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	0	0
Prior	0	5
Revolving loans	0	2
Total loans held for investment	0	7
CRE loans
Loans by origination fiscal year
Current fiscal year	1,333	873
Fiscal year before current fiscal year	789	1,244
Fiscal year two years before current fiscal year	1,075	2,167
Fiscal year three years before current fiscal year	1,874	935
Fiscal year four years before current fiscal year	599	729
Prior	1,558	1,216
Revolving loans	612	451
Total loans held for investment	7,840	7,615
Gross charge-offs
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	0	0
Prior	11	21
Revolving loans	1	0
Gross charge-offs	12	21
CRE loans | Pass
Loans by origination fiscal year
Current fiscal year	1,333	873
Fiscal year before current fiscal year	789	1,156
Fiscal year two years before current fiscal year	1,023	2,082
Fiscal year three years before current fiscal year	1,698	930
Fiscal year four years before current fiscal year	599	706
Prior	1,473	1,111
Revolving loans	612	435
Total loans held for investment	7,527	7,293
CRE loans | Special mention
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	0	30
Fiscal year two years before current fiscal year	25	76
Fiscal year three years before current fiscal year	90	0
Fiscal year four years before current fiscal year	0	14
Prior	7	16
Revolving loans	0	0
Total loans held for investment	122	136
CRE loans | Substandard
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	0	58
Fiscal year two years before current fiscal year	27	9
Fiscal year three years before current fiscal year	86	5
Fiscal year four years before current fiscal year	0	9
Prior	55	89
Revolving loans	0	16
Total loans held for investment	168	186
CRE loans | Doubtful
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	0	0
Prior	23	0
Revolving loans	0	0
Total loans held for investment	23	0
REIT loans
Loans by origination fiscal year
Current fiscal year	289	172
Fiscal year before current fiscal year	128	269
Fiscal year two years before current fiscal year	177	167
Fiscal year three years before current fiscal year	59	135
Fiscal year four years before current fiscal year	226	95
Prior	241	195
Revolving loans	570	683
Total loans held for investment	1,690	1,716
Gross charge-offs
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	0	0
Prior	0	0
Revolving loans	0	0
Gross charge-offs	0	0
REIT loans | Pass
Loans by origination fiscal year
Current fiscal year	289	172
Fiscal year before current fiscal year	128	250
Fiscal year two years before current fiscal year	158	167
Fiscal year three years before current fiscal year	59	135
Fiscal year four years before current fiscal year	113	55
Prior	241	195
Revolving loans	570	564
Total loans held for investment	1,558	1,538
REIT loans | Special mention
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	0	0
Prior	0	0
Revolving loans	0	0
Total loans held for investment	0	0
REIT loans | Substandard
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	0	19
Fiscal year two years before current fiscal year	19	0
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	113	40
Prior	0	0
Revolving loans	0	119
Total loans held for investment	132	178
REIT loans | Doubtful
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	0	0
Prior	0	0
Revolving loans	0	0
Total loans held for investment	0	0
Residential mortgage loans
Loans by origination fiscal year
Current fiscal year	1,810	1,373
Fiscal year before current fiscal year	1,206	1,637
Fiscal year two years before current fiscal year	1,465	2,734
Fiscal year three years before current fiscal year	2,518	1,494
Fiscal year four years before current fiscal year	1,390	858
Prior	1,864	1,277
Revolving loans	42	39
Total loans held for investment	10,295	9,412
Gross charge-offs
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	0	0
Prior	1	0
Revolving loans	0	0
Gross charge-offs	1	0
Residential mortgage loans | Pass
Loans by origination fiscal year
Current fiscal year	1,810	1,373
Fiscal year before current fiscal year	1,206	1,637
Fiscal year two years before current fiscal year	1,465	2,725
Fiscal year three years before current fiscal year	2,511	1,493
Fiscal year four years before current fiscal year	1,389	858
Prior	1,849	1,260
Revolving loans	42	39
Total loans held for investment	10,272	9,385
Residential mortgage loans | Special mention
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	1
Fiscal year three years before current fiscal year	1	1
Fiscal year four years before current fiscal year	1	0
Prior	3	5
Revolving loans	0	0
Total loans held for investment	5	7
Residential mortgage loans | Substandard
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	8
Fiscal year three years before current fiscal year	6	0
Fiscal year four years before current fiscal year	0	0
Prior	12	12
Revolving loans	0	0
Total loans held for investment	18	20
Residential mortgage loans | Doubtful
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	0	0
Prior	0	0
Revolving loans	0	0
Total loans held for investment	0	0
Tax-exempt loans
Loans by origination fiscal year
Current fiscal year	49	62
Fiscal year before current fiscal year	62	57
Fiscal year two years before current fiscal year	57	248
Fiscal year three years before current fiscal year	215	153
Fiscal year four years before current fiscal year	144	52
Prior	699	766
Revolving loans	0	0
Total loans held for investment	1,226	1,338
Gross charge-offs
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	0	0
Prior	0	0
Revolving loans	0	0
Gross charge-offs	0	0
Tax-exempt loans | Pass
Loans by origination fiscal year
Current fiscal year	49	62
Fiscal year before current fiscal year	62	57
Fiscal year two years before current fiscal year	57	248
Fiscal year three years before current fiscal year	215	153
Fiscal year four years before current fiscal year	144	52
Prior	699	766
Revolving loans	0	0
Total loans held for investment	1,226	1,338
Tax-exempt loans | Special mention
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	0	0
Prior	0	0
Revolving loans	0	0
Total loans held for investment	0	0
Tax-exempt loans | Substandard
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	0	0
Prior	0	0
Revolving loans	0	0
Total loans held for investment	0	0
Tax-exempt loans | Doubtful
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	0	0
Prior	0	0
Revolving loans	0	0
Total loans held for investment	$ 0	$ 0