Premises and Equipment, Net - Schedule of Premises and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 170,092	$ 144,231
Accumulated depreciation	(64,588)	(54,483)
Premises and equipment, net	105,504	89,748
Land and land improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	12,356	12,356
Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	71,919	61,409
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	20,794	15,261
Software
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 65,023	$ 55,205