Premises and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Right-of-use lease assets	$ 40,700	$ 31,348
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]
Accumulated depreciation and amortization	$ (163,728)	$ (140,450)
Total premises and equipment, net	463,924	441,692
Land
Property, Plant and Equipment [Line Items]
Premises and equipment	99,317	90,953
Buildings and improvements
Property, Plant and Equipment [Line Items]
Premises and equipment	313,884	293,338
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment	103,946	100,863
Software
Property, Plant and Equipment [Line Items]
Premises and equipment	65,855	64,877
Construction in progress
Property, Plant and Equipment [Line Items]
Premises and equipment	$ 3,950	$ 763