AVAILABLE-FOR-SALE SECURITIES, Gross Unrealized Losses and Fair Value and Significant Assumptions (Details) - Raymond James Bank - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020
Debt Securities, Available-for-sale [Line Items]
Estimated fair value less than 12 months	$ 4,721	$ 1,553
Unrealized losses less than 12 months	(50)	(5)
Estimated fair value 12 months or more	602	0
Unrealized losses 12 months or more	(19)	0
Estimated fair value	5,323	1,553
Unrealized losses	(69)	(5)
Agency residential MBS
Debt Securities, Available-for-sale [Line Items]
Estimated fair value less than 12 months	3,155	966
Unrealized losses less than 12 months	(25)	(3)
Estimated fair value 12 months or more	18	0
Unrealized losses 12 months or more	0	0
Estimated fair value	3,173	966
Unrealized losses	(25)	(3)
Agency commercial MBS
Debt Securities, Available-for-sale [Line Items]
Estimated fair value less than 12 months	645	177
Unrealized losses less than 12 months	(13)	(1)
Estimated fair value 12 months or more	353	0
Unrealized losses 12 months or more	(15)	0
Estimated fair value	998	177
Unrealized losses	(28)	(1)
Agency CMOs
Debt Securities, Available-for-sale [Line Items]
Estimated fair value less than 12 months	918	410
Unrealized losses less than 12 months	(12)	(1)
Estimated fair value 12 months or more	231	0
Unrealized losses 12 months or more	(4)	0
Estimated fair value	1,149	410
Unrealized losses	(16)	$ (1)
Other securities
Debt Securities, Available-for-sale [Line Items]
Estimated fair value less than 12 months	3
Unrealized losses less than 12 months	0
Estimated fair value 12 months or more	0
Unrealized losses 12 months or more	0
Estimated fair value	3
Unrealized losses	$ 0