Investment Securities (Details 3) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Investment Securities, Available-for-Sale, Amortized Cost
Due in one year or less	$ 6,063
Due after one year through five years	575,561
Due after five years through ten years	1,306,179
Due after ten years	3,109,167
Total	4,996,970	$ 3,688,091
Investment Securities, Available-for-Sale, Estimated Fair Value
Due in one year or less	6,091
Due after one year through five years	606,388
Due after five years through ten years	1,368,746
Due after ten years	3,254,366
Securities available‑for‑sale	$ 5,235,591	$ 3,797,187