Investment Securities - Schedule of Investment Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Available-for-sale
Amortized Cost	$ 3,547,987	$ 3,642,809
Allowance for Credit Losses	0	0
Gross Unrealized Gains	2,197	6,329
Gross Unrealized (Losses)	(397,898)	(382,917)
Estimated Fair Value	3,152,286	3,266,221
U.S. Government agencies
Available-for-sale
Amortized Cost	46,897	47,786
Allowance for Credit Losses	0	0
Gross Unrealized Gains	5	6
Gross Unrealized (Losses)	(573)	(620)
Estimated Fair Value	46,329	47,172
Mortgage-backed securities
Available-for-sale
Amortized Cost	2,317,158	2,385,646
Allowance for Credit Losses	0	0
Gross Unrealized Gains	2,096	6,072
Gross Unrealized (Losses)	(190,522)	(189,760)
Estimated Fair Value	2,128,732	2,201,958
State and political subdivisions
Available-for-sale
Amortized Cost	1,040,398	1,046,121
Allowance for Credit Losses	0	0
Gross Unrealized Gains	29	42
Gross Unrealized (Losses)	(201,547)	(187,092)
Estimated Fair Value	838,880	859,071
Other securities
Available-for-sale
Amortized Cost	143,534	163,256
Allowance for Credit Losses	0	0
Gross Unrealized Gains	67	209
Gross Unrealized (Losses)	(5,256)	(5,445)
Estimated Fair Value	$ 138,345	$ 158,020

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).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

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Amount excluding accrued interest, of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

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