AVAILABLE-FOR-SALE SECURITIES, Gross Unrealized Losses and Fair Value and Significant Assumptions (Details) - RJ Bank - USD ($) $ in Millions	Mar. 31, 2020	Sep. 30, 2019
Debt Securities, Available-for-sale [Line Items]
Estimated far value less than 12 months	$ 84	$ 313
Unrealized losses less than 12 months	(1)	(1)
Estimated fair value 12 months or more	40	509
Unrealized losses 12 months or more	0	(3)
Total estimated fair value	124	822
Total unrealized losses	(1)	(4)
Agency residential MBS
Debt Securities, Available-for-sale [Line Items]
Estimated far value less than 12 months	7	166
Unrealized losses less than 12 months	0	0
Estimated fair value 12 months or more	0	114
Unrealized losses 12 months or more	0	(1)
Total estimated fair value	7	280
Total unrealized losses	0	(1)
Agency commercial MBS
Debt Securities, Available-for-sale [Line Items]
Estimated far value less than 12 months	14	0
Unrealized losses less than 12 months	0	0
Estimated fair value 12 months or more	22	44
Unrealized losses 12 months or more	0	0
Total estimated fair value	36	44
Total unrealized losses	0	0
Agency CMOs
Debt Securities, Available-for-sale [Line Items]
Estimated far value less than 12 months	63	145
Unrealized losses less than 12 months	(1)	(1)
Estimated fair value 12 months or more	18	351
Unrealized losses 12 months or more	0	(2)
Total estimated fair value	81	496
Total unrealized losses	$ (1)	(3)
Other securities
Debt Securities, Available-for-sale [Line Items]
Estimated far value less than 12 months		2
Unrealized losses less than 12 months		0
Estimated fair value 12 months or more		0
Unrealized losses 12 months or more		0
Total estimated fair value		2
Total unrealized losses		$ 0