Securities Available-for-Sale - Estimated Fair Value of Contractual Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost [Abstract]
Maturing within one year, Amortized Cost	$ 7,155
Maturing after one year through five years, Amortized Cost	17,008
Maturing after five years through ten years, Amortized Cost	33,805
Maturing after ten years, Amortized Cost	136,057
Amortized Cost	592,378	$ 569,942
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value [Abstract]
Maturing within one year, Fair Value	7,244
Maturing after one year through five years, Fair Value	17,171
Maturing after five years through ten years, Fair Value	34,881
Maturing after ten years, Fair Value	141,114
Fair Value, Total	600,799	560,479
States and Political Subdivisions [Member]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost [Abstract]
Amortized Cost	181,900	140,181
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value [Abstract]
Fair Value, Total	188,265	140,534
Mortgage-backed Securities [Member]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost [Abstract]
Investment securities not due at a single maturity date, Amortized Cost	189,554
Amortized Cost	398,353	414,208
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value [Abstract]
Investment securities not due at a single maturity date, Fair Value	190,488
Fair Value, Total	400,389	$ 404,733
Collateralized Mortgage Obligations [Member]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost [Abstract]
Investment securities not due at a single maturity date, Amortized Cost	208,799
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value [Abstract]
Investment securities not due at a single maturity date, Fair Value	$ 209,901

Amortized cost 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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