BANK LOANS, NET, Credit Quality of Held for Investment Loan Portfolio (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
SBL
Loans by origination fiscal year
Current fiscal year	$ 133	$ 74
Fiscal year before current fiscal year	30	18
Fiscal year two years before current fiscal year	15	83
Fiscal year three years before current fiscal year	76	40
Fiscal year four years before current fiscal year	27	15
Prior	52	59
Revolving loans	15,900	14,317
Total loans held for investment	16,233	14,606
Gross charge-offs
Current fiscal year	0
Fiscal year before current fiscal year	0
Fiscal year two years before current fiscal year	0
Fiscal year three years before current fiscal year	0
Fiscal year four years before current fiscal year	0
Prior	0
Revolving loans	0
Gross charge-offs	0
SBL | Pass
Loans by origination fiscal year
Current fiscal year	131	74
Fiscal year before current fiscal year	30	18
Fiscal year two years before current fiscal year	15	83
Fiscal year three years before current fiscal year	76	40
Fiscal year four years before current fiscal year	27	15
Prior	52	59
Revolving loans	15,900	14,293
Total loans held for investment	16,231	14,582
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	0	0
Total loans held for investment	0	0
SBL | Substandard
Loans by origination fiscal year
Current fiscal year	2	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	24
Total loans held for investment	2	24
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	616	672
Fiscal year before current fiscal year	458	1,153
Fiscal year two years before current fiscal year	1,179	1,120
Fiscal year three years before current fiscal year	716	1,096
Fiscal year four years before current fiscal year	686	1,037
Prior	3,318	2,743
Revolving loans	2,980	2,585
Total loans held for investment	9,953	10,406
Gross charge-offs
Current fiscal year	0
Fiscal year before current fiscal year	0
Fiscal year two years before current fiscal year	0
Fiscal year three years before current fiscal year	3
Fiscal year four years before current fiscal year	4
Prior	38
Revolving loans	0
Gross charge-offs	45
C&I loans | Pass
Loans by origination fiscal year
Current fiscal year	616	672
Fiscal year before current fiscal year	454	1,148
Fiscal year two years before current fiscal year	1,178	1,091
Fiscal year three years before current fiscal year	716	965
Fiscal year four years before current fiscal year	586	1,020
Prior	3,287	2,675
Revolving loans	2,966	2,564
Total loans held for investment	9,803	10,135
C&I loans | Special mention
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	4	5
Fiscal year two years before current fiscal year	1	29
Fiscal year three years before current fiscal year	0	69
Fiscal year four years before current fiscal year	54	0
Prior	1	0
Revolving loans	0	4
Total loans held for investment	60	107
C&I 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	62
Fiscal year four years before current fiscal year	46	17
Prior	25	65
Revolving loans	12	17
Total loans held for investment	83	161
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	5	3
Revolving loans	2	0
Total loans held for investment	7	3
CRE loans
Loans by origination fiscal year
Current fiscal year	873	1,137
Fiscal year before current fiscal year	1,244	2,344
Fiscal year two years before current fiscal year	2,167	1,120
Fiscal year three years before current fiscal year	935	812
Fiscal year four years before current fiscal year	729	621
Prior	1,216	967
Revolving loans	451	220
Total loans held for investment	7,615	7,221
Gross charge-offs
Current fiscal year	0
Fiscal year before current fiscal year	0
Fiscal year two years before current fiscal year	0
Fiscal year three years before current fiscal year	0
Fiscal year four years before current fiscal year	0
Prior	21
Revolving loans	0
Gross charge-offs	21
CRE loans | Pass
Loans by origination fiscal year
Current fiscal year	873	1,130
Fiscal year before current fiscal year	1,156	2,344
Fiscal year two years before current fiscal year	2,082	1,115
Fiscal year three years before current fiscal year	930	766
Fiscal year four years before current fiscal year	706	604
Prior	1,111	845
Revolving loans	435	220
Total loans held for investment	7,293	7,024
CRE loans | Special mention
Loans by origination fiscal year
Current fiscal year	0	7
Fiscal year before current fiscal year	30	0
Fiscal year two years before current fiscal year	76	0
Fiscal year three years before current fiscal year	0	14
Fiscal year four years before current fiscal year	14	5
Prior	16	55
Revolving loans	0	0
Total loans held for investment	136	81
CRE loans | Substandard
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	58	0
Fiscal year two years before current fiscal year	9	5
Fiscal year three years before current fiscal year	5	32
Fiscal year four years before current fiscal year	9	12
Prior	89	67
Revolving loans	16	0
Total loans held for investment	186	116
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	0	0
Revolving loans	0	0
Total loans held for investment	0	0
REIT loans
Loans by origination fiscal year
Current fiscal year	172	258
Fiscal year before current fiscal year	269	200
Fiscal year two years before current fiscal year	167	214
Fiscal year three years before current fiscal year	135	101
Fiscal year four years before current fiscal year	95	172
Prior	195	176
Revolving loans	683	547
Total loans held for investment	1,716	1,668
Gross charge-offs
Current fiscal year	0
Fiscal year before current fiscal year	0
Fiscal year two years before current fiscal year	0
Fiscal year three years before current fiscal year	0
Fiscal year four years before current fiscal year	0
Prior	0
Revolving loans	0
Gross charge-offs	0
REIT loans | Pass
Loans by origination fiscal year
Current fiscal year	172	258
Fiscal year before current fiscal year	250	200
Fiscal year two years before current fiscal year	167	214
Fiscal year three years before current fiscal year	135	101
Fiscal year four years before current fiscal year	55	172
Prior	195	176
Revolving loans	564	547
Total loans held for investment	1,538	1,668
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	19	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	40	0
Prior	0	0
Revolving loans	119	0
Total loans held for investment	178	0
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	1,373	1,765
Fiscal year before current fiscal year	1,637	2,891
Fiscal year two years before current fiscal year	2,734	1,609
Fiscal year three years before current fiscal year	1,494	920
Fiscal year four years before current fiscal year	858	435
Prior	1,277	1,011
Revolving loans	39	31
Total loans held for investment	9,412	8,662
Gross charge-offs
Current fiscal year	0
Fiscal year before current fiscal year	0
Fiscal year two years before current fiscal year	0
Fiscal year three years before current fiscal year	0
Fiscal year four years before current fiscal year	0
Prior	0
Revolving loans	0
Gross charge-offs	0
Residential mortgage loans | Pass
Loans by origination fiscal year
Current fiscal year	1,373	1,765
Fiscal year before current fiscal year	1,637	2,889
Fiscal year two years before current fiscal year	2,725	1,607
Fiscal year three years before current fiscal year	1,493	919
Fiscal year four years before current fiscal year	858	433
Prior	1,260	992
Revolving loans	39	31
Total loans held for investment	9,385	8,636
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	1	2
Fiscal year three years before current fiscal year	1	0
Fiscal year four years before current fiscal year	0	2
Prior	5	5
Revolving loans	0	0
Total loans held for investment	7	9
Residential mortgage loans | Substandard
Loans by origination fiscal year
Current fiscal year	0	0
Fiscal year before current fiscal year	0	2
Fiscal year two years before current fiscal year	8	0
Fiscal year three years before current fiscal year	0	1
Fiscal year four years before current fiscal year	0	0
Prior	12	14
Revolving loans	0	0
Total loans held for investment	20	17
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	62	147
Fiscal year before current fiscal year	57	279
Fiscal year two years before current fiscal year	248	161
Fiscal year three years before current fiscal year	153	54
Fiscal year four years before current fiscal year	52	97
Prior	766	803
Revolving loans	0	0
Total loans held for investment	1,338	1,541
Gross charge-offs
Current fiscal year	0
Fiscal year before current fiscal year	0
Fiscal year two years before current fiscal year	0
Fiscal year three years before current fiscal year	0
Fiscal year four years before current fiscal year	0
Prior	0
Revolving loans	0
Gross charge-offs	0
Tax-exempt loans | Pass
Loans by origination fiscal year
Current fiscal year	62	147
Fiscal year before current fiscal year	57	279
Fiscal year two years before current fiscal year	248	161
Fiscal year three years before current fiscal year	153	54
Fiscal year four years before current fiscal year	52	97
Prior	766	803
Revolving loans	0	0
Total loans held for investment	1,338	1,541
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