Bank Premises and Equipment Depreciation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Bank Premises and Equipment
Depreciation expense	$ 5.7	$ 4.9	$ 4.9
Building and premises | Minimum
Bank Premises and Equipment
Building and premises and furniture, fixtures and equipment	five
Building and premises | Maximum
Bank Premises and Equipment
Building and premises and furniture, fixtures and equipment	forty
Furniture, fixtures and equipment | Minimum
Bank Premises and Equipment
Building and premises and furniture, fixtures and equipment	two
Furniture, fixtures and equipment | Maximum
Bank Premises and Equipment
Building and premises and furniture, fixtures and equipment	ten