Premises and Equipment - Summary of Premises and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 630,896	$ 601,729
Accumulated depreciation	(146,017)	(137,321)
Premises and equipment, net	484,879	464,408
Land
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	72,114	72,600
Buildings
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	384,142	373,660
Furniture, fixtures, and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	129,726	110,735
Leasehold improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 44,914	$ 44,734