Premises and Equipment - Summary of Premises and Equipment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Land	$ 9,926	$ 10,356
Buildings and building improvements	44,312	42,481
Leasehold improvements	14,017	14,260
Furniture, fixtures and equipment	35,046	31,728
Premises and equipment, gross	103,301	98,825
Less accumulated depreciation and amortization	54,806	51,217
Premises and equipment	$ 48,495	$ 47,608
Buildings and building improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	10 years
Buildings and building improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	50 years
Leasehold improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	10 years
Leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	25 years
Furniture, fixtures and equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	2 years
Furniture, fixtures and equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	30 years