Premises and Equipment - Components of Premises and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total cost	$ 97,128	$ 101,458
Less: accumulated depreciation	(40,452)	(41,899)
Net book value	56,676	59,559
Land and Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Total cost	14,292	15,683
Premises and Improvements [Member]
Property, Plant and Equipment [Line Items]
Total cost	54,158	53,707
Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Total cost	$ 28,678	$ 32,068