Investments - Schedule of Available-for-sale and Held-to-Maturity Securities Reconciliation (Details) - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	$ 2,981,667	$ 2,738,293
Gross Unrealized Gains	311	16,865
Gross Unrealized Losses	(251,382)	(100,123)
Fair Value	2,730,596	2,655,035
Debt Securities, Held-to-maturity [Abstract]
Amortized Cost	1,030,249	1,075,102
Gross Unrealized Gains	402	11,186
Gross Unrealized Losses	(116,667)	(46,474)
Fair Value	913,984	1,039,814
ACL	(165)	(145)
Total securities held-to-maturity, net	1,030,084	1,074,957
Obligations of U.S. Government-sponsored enterprises
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	143,433	187,587
Gross Unrealized Gains	0	76
Gross Unrealized Losses	(8,852)	(5,091)
Fair Value	134,581	182,572
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	642,699	626,900
Gross Unrealized Gains	0	3,914
Gross Unrealized Losses	(116,545)	(58,109)
Fair Value	526,154	572,705
Debt Securities, Held-to-maturity [Abstract]
Amortized Cost	884,514	920,199
Gross Unrealized Gains	36	10,861
Gross Unrealized Losses	(107,979)	(39,849)
Fair Value	776,571	891,211
Agency mortgage-backed securities
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	2,044,967	1,733,003
Gross Unrealized Gains	136	12,638
Gross Unrealized Losses	(125,622)	(36,330)
Fair Value	1,919,481	1,709,311
Debt Securities, Held-to-maturity [Abstract]
Amortized Cost	35,536	43,839
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(4,139)	(3,199)
Fair Value	31,397	40,640
U.S. Treasury bills
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	131,620	171,355
Gross Unrealized Gains	0	128
Gross Unrealized Losses	(312)	(499)
Fair Value	131,308	170,984
Corporate debt securities
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	18,948	19,448
Gross Unrealized Gains	175	109
Gross Unrealized Losses	(51)	(94)
Fair Value	19,072	19,463
Debt Securities, Held-to-maturity [Abstract]
Amortized Cost	110,199	111,064
Gross Unrealized Gains	366	325
Gross Unrealized Losses	(4,549)	(3,426)
Fair Value	$ 106,016	$ 107,963

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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