INVESTMENT SECURITIES - Narrative (Details)	3 Months Ended
	Mar. 31, 2023 USD ($) security	Mar. 31, 2022 USD ($)	Dec. 31, 2022 USD ($)
Debt Securities, Available-for-sale [Line Items]
Trading securities	$ 0
Number of available for sale investment securities | security	959
Number of available-for-sale securities unrealized loss position | security	953
Weighted average duration of MBS portfolio	6 years
Securities pledged as collateral	$ 3,500,000,000		$ 2,800,000,000
Sale of investment securities available-for-sale	0	$ 0
Unamortized premiums	64,100,000		66,600,000
Unaccreted discounts	24,100,000		25,200,000
Owned investment securities	4,100,000,000
Total unrealized losses on securities	671,700,000
Allowance for credit losses	0		0
Held-to-maturity debt securities with an amortized cost basis	1,100,000,000		1,100,000,000
Accrued interest	1,900,000		2,400,000
Debt securities nonaccrual	0		0
Past due held-to-maturity debt securities	1,094,808,000		1,111,629,000
Past Due
Debt Securities, Available-for-sale [Line Items]
Past due held-to-maturity debt securities	0		0
Fannie Mae (FNMA) mortgage-backed securities (MBS)
Debt Securities, Available-for-sale [Line Items]
Allowance for credit losses	0		0
Past due held-to-maturity debt securities	$ 902,774,000		$ 909,498,000