Investments - Amortized Cost and Estimated Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	$ 600,832	$ 592,378
Gross Unrealized Gains	19,569	9,956
Gross Unrealized Losses	(247)	(1,535)
Estimated Fair Value	620,154	600,799
U.S. Government Agencies [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	11,587	12,125
Gross Unrealized Gains	204	124
Gross Unrealized Losses	(49)	(104)
Estimated Fair Value	11,742	12,145
Mortgage-backed Securities [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	393,680	398,353
Gross Unrealized Gains	11,742	3,354
Gross Unrealized Losses	(176)	(1,318)
Estimated Fair Value	405,246	400,389
States and Political Subdivisions [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	195,565	181,900
Gross Unrealized Gains	7,623	6,478
Gross Unrealized Losses	(22)	(113)
Estimated Fair Value	$ 203,166	$ 188,265

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 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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-Publisher FASB
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