Investment Securities - Contractual Maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Amortized Cost
Due in one year or less	$ 33,547
Due after one year through five years	162,455
Due after five years through ten years	255,123
Due after ten years	486,703
Amortized Cost	937,828	$ 939,160
Fair Value
Due in one year or less	33,806
Due after one year through five years	166,232
Due after five years through ten years	263,149
Due after ten years	497,905
Fair Value	$ 961,092	$ 952,312