Investment Securities - Summary of Contractual Maturities of Investment Securities Classified as Available for Sale and Held to Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Available for Sale, Amortized Cost
Due in one year or less	$ 90,556
Due after one year through five years	68,557
Due after five years through ten years	38,008
Due after ten years	45,085
Total	242,206
Total securities	799,996	$ 752,260
Available for Sale, Fair Value
Due in one year or less	90,722
Due after one year through five years	70,198
Due after five years through ten years	38,964
Due after ten years	44,034
Total	243,918
Total securities	813,090	755,900
Held to Maturity, Amortized Cost
Due in one year or less	6,796
Due after one year through five years	30,495
Due after five years through ten years	6,722
Due after ten years	0
Total	44,013
Total securities	115,752	123,975
Held to Maturity, Fair Value
Due in one year or less	6,831
Due after one year through five years	31,482
Due after five years through ten years	6,765
Due after ten years	0
Total	45,078
Total securities	119,023	$ 124,904
Mortgage-backed and asset-backed securities
Available for Sale, Amortized Cost
Mortgage-backed and asset-backed securities	557,790
Available for Sale, Fair Value
Mortgage-backed and asset-backed securities	569,172
Held to Maturity, Amortized Cost
Mortgage-backed and asset-backed securities	71,739
Held to Maturity, Fair Value
Mortgage-backed and asset-backed securities	$ 73,945