Securities - Summary of Amortized Cost of Held-to Maturity Debt Securities Aggregated by Credit Quality Indicator (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Amortized Cost, Held to maturity	$ 230,505	$ 247,401
U.S. Treasury Securities [Member]
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Amortized Cost, Held to maturity	10,292	12,753
U.S. Treasury Securities [Member] | AAA / AA / A [Member]
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Amortized Cost, Held to maturity	10,292
Mortgage-Backed Securities of Government Agencies [Member]
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Amortized Cost, Held to maturity	217,656	232,068
Mortgage-Backed Securities of Government Agencies [Member] | AAA / AA / A [Member]
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Amortized Cost, Held to maturity	217,656
State and Political Subdivisions [Member]
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Amortized Cost, Held to maturity	2,557	$ 2,580
State and Political Subdivisions [Member] | AAA / AA / A [Member]
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Amortized Cost, Held to maturity	$ 2,557