Investment Securities - Summary of Contractual Maturities of Investment Securities Classified as Available for Sale and Held to Maturity (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Available for Sale, Amortized Cost
Due in one year or less	$ 82,362
Due after one year through five years	73,473
Due after five years through ten years	45,335
Due after ten years	58,229
Total	259,399
Total securities	795,559	$ 752,260
Available for Sale, Fair Value
Due in one year or less	82,477
Due after one year through five years	75,654
Due after five years through ten years	46,698
Due after ten years	58,644
Total	263,473
Total securities	811,981	755,900
Held to Maturity, Amortized Cost
Due in one year or less	13,273
Due after one year through five years	24,397
Due after five years through ten years	5,966
Due after ten years	0
Total	43,636
Total securities	109,834	123,975
Held to Maturity, Fair Value
Due in one year or less	13,394
Due after one year through five years	25,439
Due after five years through ten years	6,014
Due after ten years	0
Total	44,847
Total securities	113,241	$ 124,904
Mortgage-backed and asset-backed securities
Available for Sale, Amortized Cost
Mortgage-backed and asset-backed securities	536,160
Available for Sale, Fair Value
Mortgage-backed and asset-backed securities	548,508
Held to Maturity, Amortized Cost
Mortgage-backed and asset-backed securities	66,198
Held to Maturity, Fair Value
Mortgage-backed and asset-backed securities	$ 68,394