Securities - Summary of Gross Unrealized Losses and Fair Value of Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Total temporarily impaired securities, Available-for-sale securities, Less Than 12 Months, Fair Value		$ 2,017
Total temporarily impaired securities, Available-for-sale securities, Less Than 12 Months, Unrealized Loss		(3)
Total temporarily impaired securities, Available-for-sale securities, 12 Months or More, Fair Value	$ 2,264	32,466
Total temporarily impaired securities, Available-for-sale securities, 12 Months or More, Unrealized Loss	(11)	(273)
Total temporarily impaired securities, Available-for-sale securities, Fair Value	2,264	34,483
Total temporarily impaired securities, Available-for-sale securities, Unrealized Loss	(11)	(276)
Total temporarily impaired securities, Held-to-maturity securities, Less Than 12 Months, Fair Value	13,191	28,828
Total temporarily impaired securities, Held-to-maturity securities, Less Than 12 Months, Unrealized Loss	(994)	(69)
Total temporarily impaired securities, Held-to-maturity securities, 12 Months or More, Fair Value	5,558	99,340
Total temporarily impaired securities, Held-to-maturity securities, 12 Months or More, Unrealized Loss	(26)	(661)
Total temporarily impaired securities, Held-to-maturity securities, Fair Value	18,749	128,168
Total temporarily impaired securities, Held-to-maturity securities, Unrealized Loss	(1,020)	(730)
Residential Mortgage-Backed Securities (Issued by Government-Sponsored Entities) [Member]
Schedule Of Available For Sale Securities [Line Items]
Total temporarily impaired securities, Available-for-sale securities, Less Than 12 Months, Fair Value		2,017
Total temporarily impaired securities, Available-for-sale securities, Less Than 12 Months, Unrealized Loss		(3)
Total temporarily impaired securities, Available-for-sale securities, 12 Months or More, Fair Value	2,264	32,466
Total temporarily impaired securities, Available-for-sale securities, 12 Months or More, Unrealized Loss	(11)	(273)
Total temporarily impaired securities, Available-for-sale securities, Fair Value	2,264	34,483
Total temporarily impaired securities, Available-for-sale securities, Unrealized Loss	(11)	(276)
Total temporarily impaired securities, Held-to-maturity securities, Less Than 12 Months, Fair Value	525	26,246
Total temporarily impaired securities, Held-to-maturity securities, Less Than 12 Months, Unrealized Loss	(17)	(51)
Total temporarily impaired securities, Held-to-maturity securities, 12 Months or More, Fair Value	4,993	96,987
Total temporarily impaired securities, Held-to-maturity securities, 12 Months or More, Unrealized Loss	(3)	(639)
Total temporarily impaired securities, Held-to-maturity securities, Fair Value	5,518	123,233
Total temporarily impaired securities, Held-to-maturity securities, Unrealized Loss	(20)	(690)
Corporate [Member]
Schedule Of Available For Sale Securities [Line Items]
Total temporarily impaired securities, Held-to-maturity securities, Less Than 12 Months, Fair Value	7,190
Total temporarily impaired securities, Held-to-maturity securities, Less Than 12 Months, Unrealized Loss	(726)
Total temporarily impaired securities, Held-to-maturity securities, Fair Value	7,190
Total temporarily impaired securities, Held-to-maturity securities, Unrealized Loss	(726)
State and Political Subdivisions [Member]
Schedule Of Available For Sale Securities [Line Items]
Total temporarily impaired securities, Held-to-maturity securities, Less Than 12 Months, Fair Value	5,476	1,771
Total temporarily impaired securities, Held-to-maturity securities, Less Than 12 Months, Unrealized Loss	(251)	(4)
Total temporarily impaired securities, Held-to-maturity securities, 12 Months or More, Fair Value	565	1,354
Total temporarily impaired securities, Held-to-maturity securities, 12 Months or More, Unrealized Loss	(23)	(21)
Total temporarily impaired securities, Held-to-maturity securities, Fair Value	6,041	3,125
Total temporarily impaired securities, Held-to-maturity securities, Unrealized Loss	$ (274)	(25)
U.S. Government Sponsored Entities [Member]
Schedule Of Available For Sale Securities [Line Items]
Total temporarily impaired securities, Held-to-maturity securities, 12 Months or More, Fair Value		999
Total temporarily impaired securities, Held-to-maturity securities, 12 Months or More, Unrealized Loss		(1)
Total temporarily impaired securities, Held-to-maturity securities, Fair Value		999
Total temporarily impaired securities, Held-to-maturity securities, Unrealized Loss		(1)
Small Business Administration Loan Pools [Member]
Schedule Of Available For Sale Securities [Line Items]
Total temporarily impaired securities, Held-to-maturity securities, Less Than 12 Months, Fair Value		811
Total temporarily impaired securities, Held-to-maturity securities, Less Than 12 Months, Unrealized Loss		(14)
Total temporarily impaired securities, Held-to-maturity securities, Fair Value		811
Total temporarily impaired securities, Held-to-maturity securities, Unrealized Loss		$ (14)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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