Summary of Significant Accounting Policies - Premises and Equipment (Details)	12 Months Ended
	Dec. 31, 2019
Building and Building Improvements [Member] | Minimum [Member]
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Useful Life	25 years
Building and Building Improvements [Member] | Maximum [Member]
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Useful Life	39 years
Furniture and Fixtures [Member] | Minimum [Member]
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Furniture and Fixtures [Member] | Maximum [Member]
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Useful Life	20 years