AVAILABLE-FOR-SALE SECURITIES, Gross Unrealized Losses and Fair Value and Significant Assumptions (Details) - RJ Bank - USD ($) $ in Millions	Mar. 31, 2022	Sep. 30, 2021
Debt Securities, Available-for-sale [Line Items]
Estimated far value less than 12 months	$ 6,190	$ 4,721
Unrealized losses less than 12 months	(312)	(50)
Estimated fair value 12 months or more	2,195	602
Unrealized losses 12 months or more	(204)	(19)
Total estimated fair value	8,385	5,323
Total unrealized losses	(516)	(69)
Agency residential MBS
Debt Securities, Available-for-sale [Line Items]
Estimated far value less than 12 months	3,893	3,155
Unrealized losses less than 12 months	(193)	(25)
Estimated fair value 12 months or more	1,117	18
Unrealized losses 12 months or more	(83)	0
Total estimated fair value	5,010	3,173
Total unrealized losses	(276)	(25)
Agency commercial MBS
Debt Securities, Available-for-sale [Line Items]
Estimated far value less than 12 months	650	645
Unrealized losses less than 12 months	(36)	(13)
Estimated fair value 12 months or more	635	353
Unrealized losses 12 months or more	(78)	(15)
Total estimated fair value	1,285	998
Total unrealized losses	(114)	(28)
Agency CMOs
Debt Securities, Available-for-sale [Line Items]
Estimated far value less than 12 months	1,172	918
Unrealized losses less than 12 months	(76)	(12)
Estimated fair value 12 months or more	443	231
Unrealized losses 12 months or more	(43)	(4)
Total estimated fair value	1,615	1,149
Total unrealized losses	(119)	(16)
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
Estimated far value less than 12 months	168	3
Unrealized losses less than 12 months	(1)	0
Estimated fair value 12 months or more	0	0
Unrealized losses 12 months or more	0	0
Total estimated fair value	168	3
Total unrealized losses	(1)	$ 0
Other agency obligations
Debt Securities, Available-for-sale [Line Items]
Estimated far value less than 12 months	307
Unrealized losses less than 12 months	(6)
Estimated fair value 12 months or more	0
Unrealized losses 12 months or more	0
Total estimated fair value	307
Total unrealized losses	$ (6)