INVESTMENT SECURITIES - Narrative (Details) shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024 USD ($) security shares	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($) security shares	Jun. 30, 2023 USD ($)	Jan. 24, 2024 shares	Dec. 31, 2023 USD ($)
Schedule of Investments [Line Items]
Debt securities, available-for-sale, accrued Interest	$ 136,000,000		$ 136,000,000			$ 87,000,000
Debt Securities, held-to-maturity, accrued interest	20,000,000		20,000,000			18,000,000
Write off of accrued interest receivable	$ 0	$ 0	$ 0	$ 0
Debt securities, held-to-maturity, threshold period past due	30 days		30 days
Securities past due	$ 10,535,000,000		$ 10,535,000,000			9,979,000,000
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, number of positions | security	524		524
Securities, nonaccrual	$ 0		$ 0			0
Total Past Due
Schedule of Investments [Line Items]
Securities past due	0		0			0
Asset Pledged as Collateral
Schedule of Investments [Line Items]
Investment securities, aggregate carrying value, pledged as collateral	$ 3,890,000,000		$ 3,890,000,000			$ 3,770,000,000
Visa, Inc | Class B
Schedule of Investments [Line Items]
Investment owned (in shares) | shares	354		354
Visa, Inc | Class B-1
Schedule of Investments [Line Items]
Investment owned (in shares) | shares					354
Residential Mortgage Backed Securities or Government Agency Securities
Schedule of Investments [Line Items]
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, number of positions | security	453		453
Corporate Bonds
Schedule of Investments [Line Items]
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, number of positions | security	71		71