INVESTMENT SECURITIES - Narrative (Details) shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025 USD ($) security shares	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($) security shares	Sep. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)	Jan. 24, 2024 USD ($) shares
Schedule of Investments [Line Items]
Debt securities, available-for-sale, accrued Interest	$ 172,000,000		$ 172,000,000		$ 177,000,000
Debt Securities, held-to-maturity, accrued interest	19,000,000		19,000,000		20,000,000
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	$ 10,051,000,000		$ 10,051,000,000		10,239,000,000
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, number of positions | security	461		461
Investment securities available for sale, allowance for credit loss	$ 0		$ 0
Securities, nonaccrual	0		0		0
Asset Pledged as Collateral
Schedule of Investments [Line Items]
Investment securities, aggregate carrying value, pledged as collateral	$ 6,180,000,000		$ 6,180,000,000		3,940,000,000
Government sponsored enterprise-issued mortgage-backed securities, government agency securities, or U.S. treasury securities
Schedule of Investments [Line Items]
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, number of positions | security	427		427
Corporate bonds
Schedule of Investments [Line Items]
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, number of positions | security	34		34
Total Past Due
Schedule of Investments [Line Items]
Securities past due	$ 0		$ 0		$ 0
Visa, Inc | Class B
Schedule of Investments [Line Items]
Investment owned (in shares) | shares	354		354
Investment owned, carrying value	$ 0		$ 0
Visa, Inc | Class B-1
Schedule of Investments [Line Items]
Investment owned (in shares) | shares						354
Investment owned, carrying value						$ 0