Securities Available-for-Sale - Amortized Cost and Estimated Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	$ 592,378	$ 569,942
Gross Unrealized Gains	9,956	1,616
Gross Unrealized Losses	(1,535)	(11,079)
Estimated Fair Value	600,799	560,479
U.S. Government Agencies [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	12,125	15,553
Gross Unrealized Gains	124	12
Gross Unrealized Losses	(104)	(353)
Estimated Fair Value	12,145	15,212
Mortgage-backed Securities [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	398,353	414,208
Gross Unrealized Gains	3,354	398
Gross Unrealized Losses	(1,318)	(9,873)
Estimated Fair Value	400,389	404,733
States and Political Subdivisions [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	181,900	140,181
Gross Unrealized Gains	6,478	1,206
Gross Unrealized Losses	(113)	(853)
Estimated Fair Value	$ 188,265	$ 140,534

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).

+ References

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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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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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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-Publisher FASB
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