INVESTMENT SECURITIES - Schedule of Amortized Cost and Estimated Fair Value of Available-for-Sale and Held-to-Maturity Investment Securities (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Available-for-Sale Debt Securities
Amortized Cost	$ 4,504,342,000	$ 4,834,550,000
Gross Unrealized Gain	168,000	0
Gross Unrealized Loss	657,973,000	741,490,000
Allowance for Credit Losses	0	0
Fair Value	3,846,537,000	4,093,060,000
Held-to-Maturity Debt Securities
Amortized Cost	1,058,565,000	1,111,629,000
Gross Unrealized Gain	2,665,000	534,000
Gross Unrealized Loss	75,291,000	72,049,000
Allowance for Credit Losses	8,000	10,000
Fair Value	985,931,000	1,040,104,000
Available for sale securities transfers to held to maturity unrealized gains	(120,400,000)
Collateralized mortgage obligation (CMO)
Available-for-Sale Debt Securities
Amortized Cost	560,952,000	608,834,000
Gross Unrealized Gain	0	0
Gross Unrealized Loss	96,333,000	102,454,000
Allowance for Credit Losses	0	0
Fair Value	464,619,000	506,380,000
Fannie Mae (FNMA) mortgage-backed securities (MBS)
Available-for-Sale Debt Securities
Amortized Cost	3,544,762,000	3,823,036,000
Gross Unrealized Gain	162,000	0
Gross Unrealized Loss	502,574,000	572,778,000
Allowance for Credit Losses	0	0
Fair Value	3,042,350,000	3,250,258,000
Held-to-Maturity Debt Securities
Amortized Cost	872,653,000	909,498,000
Gross Unrealized Gain	0	0
Gross Unrealized Loss	74,332,000	68,677,000
Allowance for Credit Losses	0	0
Fair Value	798,321,000	840,821,000
Freddie Mac (FHLMC) MBS
Available-for-Sale Debt Securities
Amortized Cost	126,856,000	135,554,000
Gross Unrealized Gain	0	0
Gross Unrealized Loss	11,324,000	13,555,000
Allowance for Credit Losses	0	0
Fair Value	115,532,000	121,999,000
Ginnie Mae (GNMA) MBS
Available-for-Sale Debt Securities
Amortized Cost	46,333,000	39,116,000
Gross Unrealized Gain	6,000	0
Gross Unrealized Loss	2,999,000	2,978,000
Allowance for Credit Losses	0	0
Fair Value	43,340,000	36,138,000
Government-sponsored enterprises (GSE) agency notes
Available-for-Sale Debt Securities
Amortized Cost	225,439,000	228,010,000
Gross Unrealized Gain	0	0
Gross Unrealized Loss	44,743,000	49,725,000
Allowance for Credit Losses	0	0
Fair Value	180,696,000	178,285,000
State and political subdivisions
Held-to-Maturity Debt Securities
Amortized Cost	185,912,000	201,631,000
Gross Unrealized Gain	2,665,000	532,000
Gross Unrealized Loss	959,000	3,372,000
Allowance for Credit Losses	8,000	10,000	$ 4,000
Fair Value	$ 187,610,000	198,781,000
Available for sale securities transfers to held to maturity unrealized gains		(142,800,000)
Foreign bonds
Held-to-Maturity Debt Securities
Amortized Cost		500,000
Gross Unrealized Gain		2,000
Gross Unrealized Loss		0
Allowance for Credit Losses		0
Fair Value		$ 502,000

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Available For Sale Securities Transfers To Held To Maturity Unrealized Gains (Losses)

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