BANK LOANS, NET, Credit Quality of Held for Investment Loan Portfolio (Details) - USD ($) $ in Millions	Jun. 30, 2022	Sep. 30, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held for investment	$ 42,220	$ 25,314
C&I loans
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	694	999
Year two	1,514	1,273
Year three	1,406	1,260
Year four	1,311	1,492
Year five	1,419	961
Prior	2,299	1,715
Revolving loans	2,254	740
Total loans held for investment	10,897	8,440
C&I loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	693	999
Year two	1,514	1,273
Year three	1,341	1,180
Year four	1,244	1,408
Year five	1,370	935
Prior	2,217	1,633
Revolving loans	2,231	739
Total loans held for investment	10,610	8,167
C&I loans | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	0
Year three	62	41
Year four	38	0
Year five	0	26
Prior	82	54
Revolving loans	4	1
Total loans held for investment	186	122
C&I loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	1	0
Year two	0	0
Year three	3	24
Year four	25	84
Year five	40	0
Prior	0	28
Revolving loans	19	0
Total loans held for investment	88	136
C&I loans | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	0
Year three	0	15
Year four	4	0
Year five	9	0
Prior	0	0
Revolving loans	0	0
Total loans held for investment	13	15
CRE loans
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	1,420	533
Year two	1,331	504
Year three	923	532
Year four	796	786
Year five	971	231
Prior	724	224
Revolving loans	189	62
Total loans held for investment	6,354	2,872
CRE loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	1,420	533
Year two	1,329	459
Year three	878	442
Year four	749	652
Year five	855	223
Prior	687	174
Revolving loans	189	62
Total loans held for investment	6,107	2,545
CRE loans | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	2	45
Year three	30	58
Year four	27	36
Year five	36	0
Prior	0	0
Revolving loans	0	0
Total loans held for investment	95	139
CRE loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	0
Year three	15	32
Year four	20	98
Year five	80	8
Prior	37	50
Revolving loans	0	0
Total loans held for investment	152	188
CRE loans | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	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]
Year one	87	235
Year two	234	95
Year three	99	109
Year four	91	71
Year five	51	83
Prior	253	273
Revolving loans	601	246
Total loans held for investment	1,416	1,112
REIT loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	87	235
Year two	234	95
Year three	99	75
Year four	57	60
Year five	40	46
Prior	185	167
Revolving loans	591	237
Total loans held for investment	1,293	915
REIT loans | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	0
Year three	0	13
Year four	13	11
Year five	11	33
Prior	64	106
Revolving loans	8	6
Total loans held for investment	96	169
REIT loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	0
Year three	0	21
Year four	21	0
Year five	0	4
Prior	4	0
Revolving loans	2	3
Total loans held for investment	27	28
REIT loans | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	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]
Year one	71	158
Year two	170	57
Year three	58	124
Year four	115	204
Year five	197	272
Prior	736	506
Revolving loans	0	0
Total loans held for investment	1,347	1,321
Tax-exempt loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	71	158
Year two	170	57
Year three	58	124
Year four	115	204
Year five	197	272
Prior	736	506
Revolving loans	0	0
Total loans held for investment	1,347	1,321
Tax-exempt loans | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	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]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	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]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	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]
Year one	2,196	1,861
Year two	1,728	1,266
Year three	1,059	640
Year four	495	387
Year five	301	453
Prior	912	691
Revolving loans	37	20
Total loans held for investment	6,728	5,318
Residential mortgage loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	2,195	1,861
Year two	1,727	1,266
Year three	1,059	640
Year four	493	386
Year five	300	451
Prior	887	666
Revolving loans	37	20
Total loans held for investment	6,698	5,290
Residential mortgage loans | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	1	0
Year two	1	0
Year three	0	0
Year four	2	0
Year five	0	0
Prior	4	5
Revolving loans	0	0
Total loans held for investment	8	5
Residential mortgage loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	1
Year five	1	2
Prior	21	20
Revolving loans	0	0
Total loans held for investment	22	23
Residential mortgage loans | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior	0	0
Revolving loans	0	0
Total loans held for investment	0	0
SBL and other
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	10	3
Year two	41	45
Year three	75	12
Year four	44	0
Year five	36	0
Prior	43	0
Revolving loans	15,063	6,046
Total loans held for investment	15,312	6,106
SBL and other | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	10	3
Year two	41	45
Year three	75	12
Year four	44	0
Year five	36	0
Prior	43	0
Revolving loans	15,063	6,046
Total loans held for investment	15,312	6,106
SBL and other | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior	0	0
Revolving loans	0	0
Total loans held for investment	0	0
SBL and other | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior	0	0
Revolving loans	0	0
Total loans held for investment	0	0
SBL and other | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Prior	0	0
Revolving loans	0	0
Total loans held for investment	$ 0	$ 0