INVESTMENT SECURITIES - Narrative (Details) shares in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($) security shares	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)
Schedule of Investments [Line Items]
Debt securities, available-for-sale, accrued Interest	$ 121,000,000		$ 87,000,000
Debt Securities, held-to-maturity, accrued interest	17,000,000		18,000,000
Write off of accrued interest receivable	$ 0	$ 0
Debt securities, held-to-maturity, threshold period past due	30 days
Securities past due	$ 10,050,000,000		9,979,000,000
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, number of positions | security	504
Held-to-maturity securities, nonaccrual	$ 0		0
Total Past Due
Schedule of Investments [Line Items]
Securities past due	0		0
Asset Pledged as Collateral
Schedule of Investments [Line Items]
Investment securities, aggregate carrying value, pledged as collateral	$ 3,900,000,000		$ 3,770,000,000
Visa, Inc | Class B
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	430
Corporate Bonds
Schedule of Investments [Line Items]
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, number of positions | security	74