INVESTMENT SECURITIES - Schedule of Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Held-to-maturity
Amortized Cost		$ 3,639,850
Allowance for Credit Losses	$ 0	(3,214)	$ (3,214)
Net Carrying Amount		3,636,636
Gross Unrealized Gains		232
Gross Unrealized (Losses)		(686,917)
Estimated Fair Value		2,949,951
Available-for-sale
Amortized Cost	3,642,809	2,852,774
Allowance for Credit Losses	0	0
Gross Unrealized Gains	6,329	307
Gross Unrealized (Losses)	(382,917)	(323,655)
Estimated Fair Value	3,266,221	2,529,426
U.S. Treasury
Available-for-sale
Amortized Cost		999
Allowance for Credit Losses		0
Gross Unrealized Gains		0
Gross Unrealized (Losses)		(3)
Estimated Fair Value		996
U.S. Government agencies
Held-to-maturity
Amortized Cost		455,869
Allowance for Credit Losses		0
Net Carrying Amount		455,869
Gross Unrealized Gains		0
Gross Unrealized (Losses)		(95,961)
Estimated Fair Value		359,908
Available-for-sale
Amortized Cost	47,786	55,589
Allowance for Credit Losses	0	0
Gross Unrealized Gains	6	5
Gross Unrealized (Losses)	(620)	(1,047)
Estimated Fair Value	47,172	54,547
Mortgage-backed securities
Held-to-maturity
Amortized Cost		1,070,032
Allowance for Credit Losses		0
Net Carrying Amount		1,070,032
Gross Unrealized Gains		212
Gross Unrealized (Losses)		(133,746)
Estimated Fair Value		936,498
Available-for-sale
Amortized Cost	2,385,646	1,545,539
Allowance for Credit Losses	0	0
Gross Unrealized Gains	6,072	4
Gross Unrealized (Losses)	(189,760)	(152,784)
Estimated Fair Value	2,201,958	1,392,759
State and political subdivisions
Held-to-maturity
Amortized Cost		1,857,373
Allowance for Credit Losses	0	(196)	(2,006)
Net Carrying Amount		1,857,177
Gross Unrealized Gains		20
Gross Unrealized (Losses)		(436,061)
Estimated Fair Value		1,421,136
Available-for-sale
Amortized Cost	1,046,121	1,015,619
Allowance for Credit Losses	0	0
Gross Unrealized Gains	42	132
Gross Unrealized (Losses)	(187,092)	(157,569)
Estimated Fair Value	859,071	858,182
Other securities
Held-to-maturity
Amortized Cost		256,576
Allowance for Credit Losses	0	(3,018)	$ (1,208)
Net Carrying Amount		253,558
Gross Unrealized Gains		0
Gross Unrealized (Losses)		(21,149)
Estimated Fair Value		232,409
Available-for-sale
Amortized Cost	163,256	235,028
Allowance for Credit Losses	0	0
Gross Unrealized Gains	209	166
Gross Unrealized (Losses)	(5,445)	(12,252)
Estimated Fair Value	$ 158,020	$ 222,942

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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