Investments - Amortized Cost and Fair Value of Securities Held-to-Maturity (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Schedule of Held-to-Maturity Securities [Line Items]
Held-to-Maturity, Amortized Cost	$ 5,226	$ 2,209
Held-to-Maturity, Gross Unrecognized Gains	66	41
Held-to-Maturity, Gross Unrecognized Losses	(25)
Held-to-maturity securities	5,267	2,250
Government-Sponsored Residential Mortgage-Backed Securities [Member]
Schedule of Held-to-Maturity Securities [Line Items]
Held-to-Maturity, Amortized Cost	4,112	1,094
Held-to-Maturity, Gross Unrecognized Gains	36	3
Held-to-Maturity, Gross Unrecognized Losses	(25)
Held-to-maturity securities	4,123	1,097
State and Political Subdivisions [Member]
Schedule of Held-to-Maturity Securities [Line Items]
Held-to-Maturity, Amortized Cost	1,114	1,115
Held-to-Maturity, Gross Unrecognized Gains	30	38
Held-to-maturity securities	$ 1,144	$ 1,153