Securities - Amortized Cost and Estimated Fair Value of Securities - Securities Available-for-sale (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Securities available-for-sale:
Amortized Cost	$ 504,230	$ 505,713
Gross Unrealized (Losses)	(12,479)	(16,117)
Estimated Fair Value	491,751	489,596
U.S. Treasury
Securities available-for-sale:
Amortized Cost	430,413	428,797
Gross Unrealized (Losses)	(7,510)	(10,323)
Estimated Fair Value	422,903	418,474
Agency mortgage-backed securities
Securities available-for-sale:
Amortized Cost	73,817	76,916
Gross Unrealized (Losses)	(4,969)	(5,794)
Estimated Fair Value	$ 68,848	$ 71,122

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

+ References

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Amount 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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