Premises and Equipment - Summary of Premises and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Premises and Equipment [Line Items]
Total Cost	$ 316,548	$ 311,945
Accumulated Depreciation and Amortization	(205,486)	(198,890)
Net	111,062	113,055
Land
Premises and Equipment [Line Items]
Total Cost	25,619	25,227
Buildings and Leasehold Improvements
Premises and Equipment [Line Items]
Total Cost	163,588	162,391
Equipment
Premises and Equipment [Line Items]
Total Cost	$ 127,341	$ 124,327