Securities - Securities with Unrealized Losses Not Recognized in Income (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	$ 8,357	$ 12,600
12 Months or less, Unrealized Loss	(189)	(112)
More than 12 months, Fair Value	134	11,140
More than 12 months, Unrealized Loss	(1)	(57)
Total Fair Value	8,491	23,740
Total Unrealized Loss	(190)	(169)
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
More than 12 months, Fair Value	134	3,408
More than 12 months, Unrealized Loss	(1)	(4)
Total Fair Value	134	3,408
Total Unrealized Loss	(1)	(4)
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	5,373	1,947
12 Months or less, Unrealized Loss	(149)	(21)
Total Fair Value	5,373	1,947
Total Unrealized Loss	(149)	(21)
Mortgage-backed Securities in Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	2,984	10,653
12 Months or less, Unrealized Loss	(40)	(91)
More than 12 months, Fair Value		7,732
More than 12 months, Unrealized Loss		(53)
Total Fair Value	2,984	18,385
Total Unrealized Loss	$ (40)	$ (144)