Securities - Available for Sale Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total securities available for sale	$ 342,192	$ 343,323
Gross Unrealized Gains	16,476	4,906
Gross Unrealized Losses	(169)	(1,935)
Fair Value	358,499	346,294
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total securities available for sale	19,401	30,623
Gross Unrealized Gains	204	202
Gross Unrealized Losses	(4)	(140)
Fair Value	19,601	30,685
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total securities available for sale	193,646	168,993
Gross Unrealized Gains	12,409	3,680
Gross Unrealized Losses	(21)	(602)
Fair Value	206,034	172,071
Mortgage-back Securities in Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total securities available for sale	129,145	143,707
Gross Unrealized Gains	3,863	1,024
Gross Unrealized Losses	(144)	(1,193)
Fair Value	$ 132,864	$ 143,538

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).

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