ACQUISITIONS, Narrative (Details) £ / shares in Units, $ / shares in Units, £ in Millions, $ in Millions	Jan. 21, 2022 GBP (£) £ / shares	Jan. 21, 2022 USD ($)	Dec. 15, 2021 USD ($)	Oct. 20, 2021 USD ($) $ / shares	Dec. 31, 2021 USD ($)
TriState Capital
Business Acquisition [Line Items]
Note receivable | $			$ 125		$ 125
Note receivable interest rate, year one			2.25%
Note receivable, redemption price			100.00%
TriState Capital | SOFR
Business Acquisition [Line Items]
Note receivable, basis spread on variable rate			2.11%
Charles Stanley
Business Acquisition [Line Items]
Cash and cash equivalents segregated for regulatory purposes and restricted cash | $					$ 385
Charles Stanley | Subsequent Event
Business Acquisition [Line Items]
Share price (in dollars per share) | £ / shares	£ 5.15
Consideration	£ 274	$ 372
TriState Capital
Business Acquisition [Line Items]
Consideration | $				$ 1,100
TriState Capital | TriState Capital Common Stock
Business Acquisition [Line Items]
Cash consideration per share (in dollars per share) | $ / shares				$ 6.00
Consideration transferred, share issuance ratio				0.25
Market value of per share consideration (in dollars per share) | $ / shares				$ 31.09
TriState Capital | TriState Series C Convertible Preferred Stock
Business Acquisition [Line Items]
Cash consideration per share (in dollars per share) | $ / shares				$ 30