Premises and Equipment - Summary of Premises and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Less: accumulated depreciation	$ (60,966)	$ (56,022)
Premises and equipment, net	65,648	54,458
Land
Property, Plant and Equipment [Line Items]
Premises and equipment	11,219	9,522
Buildings
Property, Plant and Equipment [Line Items]
Premises and equipment	40,947	31,376
Furniture and equipment.
Property, Plant and Equipment [Line Items]
Premises and equipment	44,862	38,775
Leasehold improvements
Property, Plant and Equipment [Line Items]
Premises and equipment	25,186	26,636
Construction in progress
Property, Plant and Equipment [Line Items]
Premises and equipment	$ 4,400	$ 4,171