Investment and Equity Securities - Amortized Cost and Fair Value of Available for Sale Securities Portfolio (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Investments Debt And Equity Securities [Abstract]
Due within twelve months, Amortized cost	$ 4,168
Due after one but within five years, Amortized Cost	45,995
Due after five but within ten years, Amortized Cost	86,917
Due after ten years, Amortized Cost	229,412
Available-for-sale Securities, Amortized Cost	366,492	$ 365,936
Due within twelve months, Estimated Fair Value	4,111
Due after one but within five years, Estimated Fair Value	44,363
Due after five but within ten years, Estimated Fair Value	77,384
Due after ten years, Estimated Fair Value	205,296
Available-for-sale Securities, Estimated Fair Value	$ 331,154	$ 324,683
Due within twelve months, Book Yield	7.31%
Due after one but within five years, Book Yield	3.14%
Due after five but within ten years, Book Yield	2.12%
Due after ten years, Book Yield	3.17%
Total securities available for sale, Book Yield	2.97%