Investment Securities - Contractual Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Amortized Cost
Due in one year or less	$ 18,745
Due after one year through five years	174,623
Due after five years through ten years	293,616
Due after ten years	452,176
Amortized Cost	939,160
Fair Value
Due in one year or less	18,888
Due after one year through five years	176,734
Due after five years through ten years	298,650
Due after ten years	458,040
Fair Value	$ 952,312	$ 976,095