AVAILABLE-FOR-SALE SECURITIES, Gross Unrealized Losses and Fair Value and Significant Assumptions (Details) - Bank - USD ($) $ in Millions	Sep. 30, 2022	Sep. 30, 2021
Debt Securities, Available-for-sale [Line Items]
Estimated fair value less than 12 months	$ 5,156	$ 4,721
Unrealized losses less than 12 months	(405)	(50)
Estimated fair value 12 months or more	4,716	602
Unrealized losses 12 months or more	(810)	(19)
Estimated fair value	9,872	5,323
Unrealized losses	(1,215)	(69)
Agency residential MBS
Debt Securities, Available-for-sale [Line Items]
Estimated fair value less than 12 months	2,165	3,155
Unrealized losses less than 12 months	(226)	(25)
Estimated fair value 12 months or more	2,829	18
Unrealized losses 12 months or more	(442)	0
Estimated fair value	4,994	3,173
Unrealized losses	(668)	(25)
Agency commercial MBS
Debt Securities, Available-for-sale [Line Items]
Estimated fair value less than 12 months	494	645
Unrealized losses less than 12 months	(41)	(13)
Estimated fair value 12 months or more	816	353
Unrealized losses 12 months or more	(167)	(15)
Estimated fair value	1,310	998
Unrealized losses	(208)	(28)
Agency CMOs
Debt Securities, Available-for-sale [Line Items]
Estimated fair value less than 12 months	337	918
Unrealized losses less than 12 months	(32)	(12)
Estimated fair value 12 months or more	1,067	231
Unrealized losses 12 months or more	(201)	(4)
Estimated fair value	1,404	1,149
Unrealized losses	(233)	(16)
Other agency obligations
Debt Securities, Available-for-sale [Line Items]
Estimated fair value less than 12 months	582
Unrealized losses less than 12 months	(31)
Estimated fair value 12 months or more	0
Unrealized losses 12 months or more	0
Estimated fair value	582
Unrealized losses	(31)
Non-agency residential MBS
Debt Securities, Available-for-sale [Line Items]
Estimated fair value less than 12 months	451
Unrealized losses less than 12 months	(41)
Estimated fair value 12 months or more	0
Unrealized losses 12 months or more	0
Estimated fair value	451
Unrealized losses	(41)
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
Estimated fair value less than 12 months	982	3
Unrealized losses less than 12 months	(28)	0
Estimated fair value 12 months or more	4	0
Unrealized losses 12 months or more	0	0
Estimated fair value	986	3
Unrealized losses	(28)	$ 0
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Estimated fair value less than 12 months	128
Unrealized losses less than 12 months	(5)
Estimated fair value 12 months or more	0
Unrealized losses 12 months or more	0
Estimated fair value	128
Unrealized losses	(5)
Other
Debt Securities, Available-for-sale [Line Items]
Estimated fair value less than 12 months	17
Unrealized losses less than 12 months	(1)
Estimated fair value 12 months or more	0
Unrealized losses 12 months or more	0
Estimated fair value	17
Unrealized losses	$ (1)