Securities - Summary of Amortized Cost and Fair Value of Debt Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Available-for-sale
Due in one year or less, Amortized Cost	$ 1,443
Due after one through five years, Amortized Cost	23,486
Due after five through ten years, Amortized Cost	32,930
Due after ten years, Amortized Cost	129,019
Amortized Cost, Available-for-sale	186,878	$ 189,072
Due in one year or less, Fair Value	1,445
Due after one through five years, Fair Value	23,623
Due after five through ten years, Fair Value	32,813
Due after ten years, Fair Value	127,573
Total debt securities available-for-sale, Fair Value	185,454	190,438
Held-to-maturity
Due after five through ten years, Amortized Cost	500
Due after ten years, Amortized Cost	50,817
Amortized Cost, Held to maturity	51,317	9,045
Due after five through ten years, Fair Value	501
Due after ten years, Fair Value	50,512
Total debt securities held-to-maturity, Fair Value	$ 51,013	$ 9,225