Securities - Schedule of AFS Debt Securities, By Maturity Date (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Amortized Cost
Within one year	$ 6,254
After one year but within five years	41,179
After five years but within ten years	51,448
After ten years	360,762
Amortized Cost	459,643	$ 335,603
Fair Value
Within one year	6,281
After one year but within five years	42,008
After five years but within ten years	53,043
After ten years	366,412
Fair Value	$ 467,744