Premises and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 553,253	$ 557,103
Less: Accumulated depreciation and amortization	(321,773)	(317,057)
Premises and equipment, net	231,480	240,046
Land
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	38,654	38,836
Buildings and improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	343,604	350,609
Furniture and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	165,572	158,064
Construction in progress
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 5,423	$ 9,594