BANK LOANS, NET, Credit Quality of Held for Investment Loan Portfolio (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
SBL
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	$ 74	$ 14
Fiscal year before current fiscal year	18	27
Fiscal year two years before current fiscal year	83	72
Fiscal year three years before current fiscal year	40	44
Fiscal year four years before current fiscal year	15	36
Prior	59	41
Revolving loans	14,317	15,063
Total loans held for investment	14,606	15,297
SBL | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	74	14
Fiscal year before current fiscal year	18	27
Fiscal year two years before current fiscal year	83	72
Fiscal year three years before current fiscal year	40	44
Fiscal year four years before current fiscal year	15	36
Prior	59	41
Revolving loans	14,293	15,063
Total loans held for investment	14,582	15,297
SBL | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
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
Financing Receivable, Credit Quality Indicator [Line Items]
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	24	0
Total loans held for investment	24	0
SBL | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
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
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	672	1,022
Fiscal year before current fiscal year	1,153	1,476
Fiscal year two years before current fiscal year	1,120	1,364
Fiscal year three years before current fiscal year	1,096	1,189
Fiscal year four years before current fiscal year	1,037	1,434
Prior	2,743	2,288
Revolving loans	2,585	2,400
Total loans held for investment	10,406	11,173
C&I loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	672	1,011
Fiscal year before current fiscal year	1,148	1,448
Fiscal year two years before current fiscal year	1,091	1,301
Fiscal year three years before current fiscal year	965	1,124
Fiscal year four years before current fiscal year	1,020	1,389
Prior	2,675	2,200
Revolving loans	2,564	2,380
Total loans held for investment	10,135	10,853
C&I loans | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	10
Fiscal year before current fiscal year	5	28
Fiscal year two years before current fiscal year	29	3
Fiscal year three years before current fiscal year	69	37
Fiscal year four years before current fiscal year	0	0
Prior	0	82
Revolving loans	4	6
Total loans held for investment	107	166
C&I loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	1
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	0	60
Fiscal year three years before current fiscal year	62	28
Fiscal year four years before current fiscal year	17	40
Prior	65	6
Revolving loans	17	14
Total loans held for investment	161	149
C&I loans | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
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	5
Prior	3	0
Revolving loans	0	0
Total loans held for investment	3	5
CRE loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,137	1,916
Fiscal year before current fiscal year	2,344	1,346
Fiscal year two years before current fiscal year	1,120	906
Fiscal year three years before current fiscal year	812	724
Fiscal year four years before current fiscal year	621	898
Prior	967	583
Revolving loans	220	176
Total loans held for investment	7,221	6,549
CRE loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,130	1,916
Fiscal year before current fiscal year	2,344	1,345
Fiscal year two years before current fiscal year	1,115	892
Fiscal year three years before current fiscal year	766	707
Fiscal year four years before current fiscal year	604	816
Prior	845	551
Revolving loans	220	176
Total loans held for investment	7,024	6,403
CRE loans | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	7	0
Fiscal year before current fiscal year	0	1
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	14	0
Fiscal year four years before current fiscal year	5	36
Prior	55	2
Revolving loans	0	0
Total loans held for investment	81	39
CRE loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Fiscal year two years before current fiscal year	5	14
Fiscal year three years before current fiscal year	32	17
Fiscal year four years before current fiscal year	12	46
Prior	67	30
Revolving loans	0	0
Total loans held for investment	116	107
CRE loans | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
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
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	258	169
Fiscal year before current fiscal year	200	230
Fiscal year two years before current fiscal year	214	96
Fiscal year three years before current fiscal year	101	53
Fiscal year four years before current fiscal year	172	40
Prior	176	222
Revolving loans	547	782
Total loans held for investment	1,668	1,592
REIT loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	258	169
Fiscal year before current fiscal year	200	230
Fiscal year two years before current fiscal year	214	96
Fiscal year three years before current fiscal year	101	53
Fiscal year four years before current fiscal year	172	40
Prior	176	222
Revolving loans	547	782
Total loans held for investment	1,668	1,592
REIT loans | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
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
Financing Receivable, Credit Quality Indicator [Line Items]
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 | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
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
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,765	2,986
Fiscal year before current fiscal year	2,891	1,705
Fiscal year two years before current fiscal year	1,609	1,023
Fiscal year three years before current fiscal year	920	479
Fiscal year four years before current fiscal year	435	291
Prior	1,011	867
Revolving loans	31	35
Total loans held for investment	8,662	7,386
Residential mortgage loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,765	2,984
Fiscal year before current fiscal year	2,889	1,704
Fiscal year two years before current fiscal year	1,607	1,023
Fiscal year three years before current fiscal year	919	477
Fiscal year four years before current fiscal year	433	290
Prior	992	843
Revolving loans	31	35
Total loans held for investment	8,636	7,356
Residential mortgage loans | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	1
Fiscal year before current fiscal year	0	1
Fiscal year two years before current fiscal year	2	0
Fiscal year three years before current fiscal year	0	2
Fiscal year four years before current fiscal year	2	0
Prior	5	4
Revolving loans	0	0
Total loans held for investment	9	8
Residential mortgage loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	1
Fiscal year before current fiscal year	2	0
Fiscal year two years before current fiscal year	0	0
Fiscal year three years before current fiscal year	1	0
Fiscal year four years before current fiscal year	0	1
Prior	14	20
Revolving loans	0	0
Total loans held for investment	17	22
Residential mortgage loans | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
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
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	147	264
Fiscal year before current fiscal year	279	169
Fiscal year two years before current fiscal year	161	56
Fiscal year three years before current fiscal year	54	115
Fiscal year four years before current fiscal year	97	192
Prior	803	705
Revolving loans	0	0
Total loans held for investment	1,541	1,501
Tax-exempt loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	147	264
Fiscal year before current fiscal year	279	169
Fiscal year two years before current fiscal year	161	56
Fiscal year three years before current fiscal year	54	115
Fiscal year four years before current fiscal year	97	192
Prior	803	705
Revolving loans	0	0
Total loans held for investment	1,541	1,501
Tax-exempt loans | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
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
Financing Receivable, Credit Quality Indicator [Line Items]
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
Financing Receivable, Credit Quality Indicator [Line Items]
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