Securities - Amortized Cost and Fair Value of Debt Securities by Contractual Maturity - Securities Held-to-maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Held-to-maturity, Amortized Cost
Due 3 months or less	$ 530
Due after 3 months through one year	914
Due after one year through five years	7,283
Due after five years through ten years	33,354
Due after ten years	31,581
Agency mortgage-backed securities	249,070
Total	322,732
Held-to-maturity, Estimated Fair Value
Due 3 months or less	531
Due after 3 months through one year	917
Due after one year through five years	7,537
Due after five years through ten years	34,201
Due after ten years	32,302
Agency mortgage-backed securities	256,964
Total	$ 332,452	$ 368,107