Securities - Schedule of AFS Debt Securities, By Maturity Date (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Amortized Cost
Within one year	$ 5,353
After one year but within five years	41,965
After five years but within ten years	51,485
After ten years	390,642
Amortized Cost	489,445	$ 335,603
Fair Value
Within one year	5,372
After one year but within five years	42,806
After five years but within ten years	53,125
After ten years	396,903
Fair Value	$ 498,206	$ 335,573