Summary of Significant Accounting Policies - Concentrations of Credit Risk (Details) - Concentrations of Credit Risk $ in Millions	Dec. 31, 2019 USD ($) item
Concentrations of Credit Risk
Concentration risk threshold, total risk-based capital threshold (as a percent)	25.00%
Concentration risk threshold, total risk-based capital threshold	$ 375.3
Number of credit concentrations for non-acquired credit impaired loans | item	4
Lessors of residential and buildings
Concentrations of Credit Risk
Concentration risk threshold, total risk-based capital threshold	$ 570.9
Lessors of nonresidential buildings
Concentrations of Credit Risk
Concentration risk threshold, total risk-based capital threshold	1,400.0
Loans on hotels and motels
Concentrations of Credit Risk
Concentration risk threshold, total risk-based capital threshold	574.6
Loans on owner occupied office buildings
Concentrations of Credit Risk
Concentration risk threshold, total risk-based capital threshold	$ 380.5