ALLOWANCE FOR CREDIT LOSSES - Expected Credit Loss of Accounts Payable (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022	Dec. 31, 2021
Contract with Customer, Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 17	$ 18	$ 17	$ 18	$ 20	$ 18	$ 18	$ 40
Provision for credit losses	4	9	19	28
Ending balance	17	$ 18	17	$ 18
Credit Card Receivable
Contract with Customer, Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	22		22			$ 0
Opening balance from acquisition of Robinhood Credit			16
Provision for credit losses			10
Payments to Coastal Bank			(4)
Ending balance	$ 22		$ 22