Investment Securities - Unrealized Gain (Loss) on Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Available-for-sale
Amortized Cost	$ 249,736	$ 262,342
Gross Unrealized Gains	0	0
Gross Unrealized Losses	31,672	24,464
Estimated Fair Value	218,064	237,878
Held-to-maturity
Amortized Cost	401,561	399,494
Gross Unrealized Gains	0	0
Gross Unrealized Losses	60,555	50,989
Estimated Fair Value	341,006	348,505
Amortized Cost	651,297	661,836
Gross Unrealized Gains	0	0
Gross Unrealized Losses	92,227	75,453
Estimated Fair Value	559,070	586,383
U.S. Treasury and U.S. government agencies
Available-for-sale
Amortized Cost	36,609	36,528
Gross Unrealized Gains	0	0
Gross Unrealized Losses	1,878	1,614
Estimated Fair Value	34,731	34,914
Held-to-maturity
Amortized Cost	245,771	245,671
Gross Unrealized Gains	0	0
Gross Unrealized Losses	40,363	34,834
Estimated Fair Value	205,408	210,837
Mortgage-backed U.S. government agencies
Available-for-sale
Amortized Cost	173,060	185,993
Gross Unrealized Gains	0	0
Gross Unrealized Losses	24,416	19,078
Estimated Fair Value	148,644	166,915
Held-to-maturity
Amortized Cost	45,374	50,710
Gross Unrealized Gains	0	0
Gross Unrealized Losses	7,614	6,676
Estimated Fair Value	37,760	44,034
State and political subdivision obligations
Available-for-sale
Amortized Cost	4,338	4,354
Gross Unrealized Gains	0	0
Gross Unrealized Losses	1,026	815
Estimated Fair Value	3,312	3,539
Held-to-maturity
Amortized Cost	84,942	87,125
Gross Unrealized Gains	0	0
Gross Unrealized Losses	11,330	8,345
Estimated Fair Value	73,612	78,780
Corporate debt securities
Available-for-sale
Amortized Cost	35,729	35,467
Gross Unrealized Gains	0	0
Gross Unrealized Losses	4,352	2,957
Estimated Fair Value	31,377	32,510
Held-to-maturity
Amortized Cost	25,474	15,988
Gross Unrealized Gains	0	0
Gross Unrealized Losses	1,248	1,134
Estimated Fair Value	$ 24,226	$ 14,854

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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Amortized cost excluding accrued interest, before allowance for credit loss, of 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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Amortized cost, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity) and 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 of cumulative unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity) and 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 of cumulative unrecognized loss on investment in debt security measured at amortized cost (held-to-maturity) and 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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Fair value of investment in debt security measured at amortized cost (held-to-maturity) and 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 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).

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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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Amount of accumulated unrealized loss 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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