SECURITIES - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Accrued interest receivable on debt securities	$ 125,000,000	$ 107,000,000
Taxable interest income from investment securities	1,200,000,000	840,000,000	$ 487,000,000
Offsetting of short-term receivables or payables recognized	$ 0	0
Held-to-maturity, zero expected credit loss, percent of portfolio	95.00%
Total mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Securitizations of mortgage loans	$ 102,000,000	$ 143,000,000