Investment Securities - Amortized Cost and Fair Value of Investment Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Amortized Cost
Due in one year or less	$ 145
Due after one year through five years	3,633
Due after five years through ten years	723
Due after ten years	3,802
Debt Securities With Single Maturity Date, Amortized Cost	8,303
Mortgage-backed securities	318,115
Amortized cost	326,418	$ 346,874
Fair Value
Due In One Year or Less	147
Due After One Year Through Five Years	3,640
Due After Five Years Through Ten Years	761
Due After Ten Years	3,879
Debt Securities With Single Maturity Date, Fair Value	8,427
Mortgage-Backed Securities	324,658
Fair Value	$ 333,085	$ 347,332