Premises and Equipment Premises and Equipment (Additional Information) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	$ 35,324	$ 33,133
Gain (Loss) on Disposition of Property Plant Equipment	0	0	$ 0
Software and Software Development Costs [Member]
Property, Plant and Equipment [Line Items]
Capitalized Computer Software, Gross	2,300
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	$ 2,200	$ 2,100