Investment Securities - Summary of Contractual Maturities of Investment Securities Classified as Available for Sale and Held to Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Available for Sale, Amortized Cost
Due in one year or less	$ 57,725
Due after one year through five years	228,358
Due after five years through ten years	136,143
Due after ten years	58,274
Total	480,500
Total	1,061,596	$ 1,158,534
Available for Sale, Fair Value
Due in one year or less	56,140
Due after one year through five years	211,652
Due after five years through ten years	115,478
Due after ten years	51,324
Total	434,594
Total	942,510	1,054,312
Held to Maturity, Amortized Cost
Due in one year or less	19,963
Due after one year through five years	36,981
Due after five years through ten years	96,873
Due after ten years	337,103
Total	490,920
Amortized Cost	847,845	923,415
Held to Maturity, Fair Value
Due in one year or less	19,882
Due after one year through five years	34,401
Due after five years through ten years	78,179
Due after ten years	242,400
Total	374,862
Total	656,725	$ 760,455
Mortgage-backed and asset-backed securities
Available for Sale, Amortized Cost
Mortgage-backed and asset-backed securities	581,096
Available for Sale, Fair Value
Mortgage-backed and asset-backed securities	507,916
Held to Maturity, Amortized Cost
Mortgage-backed and asset-backed securities	356,925
Held to Maturity, Fair Value
Mortgage-backed and asset-backed securities	$ 281,863