Premises and Equipment - Summary of Premises and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Less: Accumulated depreciation	$ (57,462)	$ (53,704)
Premises and equipment, net	83,731	87,086
Depreciable premises and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	140,833	140,417
Premises and equipment, net	83,371	86,713
Land and land improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	29,505	29,453
Buildings
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	65,334	65,241
Furniture and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	45,994	45,723
Construction in progress
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 360	$ 373