Investment Securities - Amortized Cost and Fair Value Held-to-Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Held-to-Maturity
Allowance for securities held-to-maturity	$ (150)	$ (150)
Total held-to-maturity securities	2,910,215	2,954,881
Unrealized Gains	182	317
Unrealized Losses	(391,725)	(484,060)
Fair Value	2,518,672	2,471,138
U.S. government-sponsored entities and agencies
Held-to-Maturity
Amortized Cost	838,535	832,984
Unrealized Gains	0	0
Unrealized Losses	(132,641)	(168,653)
Fair Value	705,894	664,331
Mortgage-backed securities
Held-to-Maturity
Amortized Cost	925,192	970,212
Unrealized Gains	0	0
Unrealized Losses	(130,879)	(169,546)
Fair Value	794,313	800,666
States and political subdivisions
Held-to-Maturity
Amortized Cost	1,146,638	1,151,835
Unrealized Gains	182	317
Unrealized Losses	(128,205)	(145,861)
Fair Value	$ 1,018,615	$ 1,006,291

Amount, excluding accrued interest, of allowance for credit loss on investment in debt security measured at amortized cost (held-to-maturity).

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Amount excluding accrued interest, after allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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