Investment Securities - Amortized Cost and Fair Value of Investment Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Amortized Cost
Due in one year or less	$ 894
Due after one year through five years	3,956
Due after five years through ten years	4,346
Due after ten years	23,344
Debt Securities With Single Maturity Date, Amortized Cost	32,540
Mortgage-backed securities	332,208
Amortized cost	364,748	$ 346,874
Fair Value
Due In One Year or Less	897
Due After One Year Through Five Years	3,989
Due After Five Years Through Ten Years	4,421
Due After Ten Years	23,644
Debt Securities With Single Maturity Date, Fair Value	32,951
Mortgage-Backed Securities	340,659
Fair Value	$ 373,610	$ 347,332