Premises and Equipment - Summary of Premises and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 89,942	$ 93,359
Less: accumulated depreciation	40,022	42,644
Premises and equipment, net	49,920	50,715
Land
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	8,301	8,147
Premises and leasehold improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	52,810	53,903
Furniture and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	27,548	31,238
Construction in process
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 1,283	$ 71