Securities - Available for Sale Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total securities available for sale	$ 336,152	$ 343,323
Gross Unrealized Gains	19,269	4,906
Gross Unrealized Losses	(134)	(1,935)
Fair Value	355,287	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	21,534	30,623
Gross Unrealized Gains	216	202
Gross Unrealized Losses	(13)	(140)
Fair Value	21,737	30,685
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total securities available for sale	179,954	168,993
Gross Unrealized Gains	14,314	3,680
Gross Unrealized Losses	(13)	(602)
Fair Value	194,255	172,071
Mortgage-backed Securities in Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total securities available for sale	134,664	143,707
Gross Unrealized Gains	4,739	1,024
Gross Unrealized Losses	(108)	(1,193)
Fair Value	$ 139,295	$ 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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