ALLOWANCE FOR CREDIT LOSSES AND CREDIT CARD EXPECTED LOSS LIABILITY - Expected Credit Loss of Accounts Payable (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Off-Balance-Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	$ 32	$ 0
Opening balance from acquisition of Robinhood Credit	23
Provision for credit losses	19
Payments to Coastal Bank	(11)
Recoveries	1
Ending balance	$ 32