INVESTMENT SECURITIES - Gains (Losses) Within Investment Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Gross gains on investment securities	$ 0	$ 15	$ 2	$ 15
Gross losses on investment securities	(1)	0	(2)	(61)
Gross gains on equity securities	0	0	0	1
Gross losses on equity securities	0	0	0	0
Net recognized (losses) gains on investment securities	$ (1)	$ 15	$ 0	$ (45)