Securities - Available for Sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total securities available for sale	$ 343,638	$ 342,192
Gross Unrealized Gains	24,763	16,476
Gross Unrealized Losses	(18)	(169)
Fair Value	368,383	358,499
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	19,124	19,401
Gross Unrealized Gains	377	204
Gross Unrealized Losses	(1)	(4)
Fair Value	19,500	19,601
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total securities available for sale	206,192	193,646
Gross Unrealized Gains	18,139	12,409
Gross Unrealized Losses	(12)	(21)
Fair Value	224,319	206,034
Mortgage-backed Securities in Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total securities available for sale	118,322	129,145
Gross Unrealized Gains	6,247	3,863
Gross Unrealized Losses	(5)	(144)
Fair Value	$ 124,564	$ 132,864

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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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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