BANK LOANS, NET, Credit Quality of Held for Investment Loan Portfolio (Details) - USD ($) $ in Millions	Dec. 31, 2022	Sep. 30, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held for investment	$ 44,474	$ 43,635
SBL
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	5	14
Fiscal year before current fiscal year	14	27
Fiscal year two years before current fiscal year	79	72
Fiscal year three years before current fiscal year	54	44
Fiscal year four years before current fiscal year	27	36
Prior	93	41
Revolving loans	14,613	15,063
Total loans held for investment	14,885	15,297
SBL | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	5	14
Fiscal year before current fiscal year	14	27
Fiscal year two years before current fiscal year	79	72
Fiscal year three years before current fiscal year	54	44
Fiscal year four years before current fiscal year	27	36
Prior	93	41
Revolving loans	14,613	15,063
Total loans held for investment	14,885	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	0	0
Total loans held for investment	0	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	187	1,022
Fiscal year before current fiscal year	1,139	1,476
Fiscal year two years before current fiscal year	1,447	1,364
Fiscal year three years before current fiscal year	1,392	1,189
Fiscal year four years before current fiscal year	1,106	1,434
Prior	3,496	2,288
Revolving loans	2,638	2,400
Total loans held for investment	11,405	11,173
C&I loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	187	1,011
Fiscal year before current fiscal year	1,129	1,448
Fiscal year two years before current fiscal year	1,418	1,301
Fiscal year three years before current fiscal year	1,295	1,124
Fiscal year four years before current fiscal year	1,074	1,389
Prior	3,372	2,200
Revolving loans	2,620	2,380
Total loans held for investment	11,095	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	10	28
Fiscal year two years before current fiscal year	29	3
Fiscal year three years before current fiscal year	38	37
Fiscal year four years before current fiscal year	9	0
Prior	75	82
Revolving loans	5	6
Total loans held for investment	166	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	59	28
Fiscal year four years before current fiscal year	23	40
Prior	45	6
Revolving loans	13	14
Total loans held for investment	140	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
Fiscal year three years before current fiscal year	0	0
Fiscal year four years before current fiscal year	0	5
Prior	4	0
Revolving loans	0	0
Total loans held for investment	4	5
CRE loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	389	1,916
Fiscal year before current fiscal year	2,362	1,346
Fiscal year two years before current fiscal year	1,207	906
Fiscal year three years before current fiscal year	829	724
Fiscal year four years before current fiscal year	678	898
Prior	1,303	583
Revolving loans	161	176
Total loans held for investment	6,929	6,549
CRE loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	384	1,916
Fiscal year before current fiscal year	2,362	1,345
Fiscal year two years before current fiscal year	1,206	892
Fiscal year three years before current fiscal year	812	707
Fiscal year four years before current fiscal year	665	816
Prior	1,232	551
Revolving loans	161	176
Total loans held for investment	6,822	6,403
CRE loans | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	5	0
Fiscal year before current fiscal year	0	1
Fiscal year two years before current fiscal year	1	0
Fiscal year three years before current fiscal year	14	0
Fiscal year four years before current fiscal year	0	36
Prior	38	2
Revolving loans	0	0
Total loans held for investment	58	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	0	14
Fiscal year three years before current fiscal year	3	17
Fiscal year four years before current fiscal year	13	46
Prior	33	30
Revolving loans	0	0
Total loans held for investment	49	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	213	169
Fiscal year before current fiscal year	226	230
Fiscal year two years before current fiscal year	217	96
Fiscal year three years before current fiscal year	100	53
Fiscal year four years before current fiscal year	54	40
Prior	202	222
Revolving loans	668	782
Total loans held for investment	1,680	1,592
REIT loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	213	169
Fiscal year before current fiscal year	226	230
Fiscal year two years before current fiscal year	217	96
Fiscal year three years before current fiscal year	100	53
Fiscal year four years before current fiscal year	54	40
Prior	202	222
Revolving loans	668	782
Total loans held for investment	1,680	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
Tax-exempt loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	165	264
Fiscal year before current fiscal year	297	169
Fiscal year two years before current fiscal year	169	56
Fiscal year three years before current fiscal year	56	115
Fiscal year four years before current fiscal year	109	192
Prior	871	705
Revolving loans	0	0
Total loans held for investment	1,667	1,501
Tax-exempt loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	165	264
Fiscal year before current fiscal year	297	169
Fiscal year two years before current fiscal year	169	56
Fiscal year three years before current fiscal year	56	115
Fiscal year four years before current fiscal year	109	192
Prior	871	705
Revolving loans	0	0
Total loans held for investment	1,667	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
Residential mortgage loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	538	2,986
Fiscal year before current fiscal year	2,990	1,705
Fiscal year two years before current fiscal year	1,673	1,023
Fiscal year three years before current fiscal year	989	479
Fiscal year four years before current fiscal year	468	291
Prior	1,118	867
Revolving loans	42	35
Total loans held for investment	7,818	7,386
Residential mortgage loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	538	2,984
Fiscal year before current fiscal year	2,988	1,704
Fiscal year two years before current fiscal year	1,672	1,023
Fiscal year three years before current fiscal year	989	477
Fiscal year four years before current fiscal year	466	290
Prior	1,093	843
Revolving loans	42	35
Total loans held for investment	7,788	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	1	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	8	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	0	0
Fiscal year four years before current fiscal year	0	1
Prior	20	20
Revolving loans	0	0
Total loans held for investment	22	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