INVESTMENT SECURITIES - Narrative (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2025 USD ($) security	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($) security	Jun. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)
Schedule of Investments [Line Items]
Trading securities	$ 0		$ 0
Number of available for sale investment securities | security	1,001		1,001
Number of available-for-sale securities unrealized loss position | security	961		961
Weighted average duration of MBS portfolio			6 years 2 months 12 days
Securities pledged as collateral	$ 3,500,000,000		$ 3,500,000,000		$ 3,300,000,000
Sale of investment securities available-for-sale			0	$ 0
Unamortized premiums	44,200,000		44,200,000		48,100,000
Unaccreted discounts	16,500,000		16,500,000		17,600,000
Allowance for credit losses	0		0		0
Held-to-maturity debt securities with an amortized cost basis	1,000,000,000.0		1,000,000,000.0		1,000,000,000.0
Accrued interest	3,500,000		3,500,000		3,600,000
Debt securities nonaccrual	0		0		0
Past due held-to-maturity debt securities	994,346,000		994,346,000		1,015,168,000
Fair value	17,800,000		17,800,000		18,200,000
Realized gain on sale of equity investments, net	18,000	$ 2,130,000	18,000	$ 2,130,000
Maximum
Schedule of Investments [Line Items]
Realized gain on sale of equity investments, net	100,000		100,000
Past Due
Schedule of Investments [Line Items]
Past due held-to-maturity debt securities	$ 0		$ 0		$ 0