Investment Securities (Details 2) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Investment Securities, Available-for-Sale, Amortized Cost
Due in one year or less	$ 37,197
Due after one year through five years	749,860
Due after five years through ten years	991,138
Due after ten years	2,239,714
Total	4,017,909	$ 3,721,525
Investment Securities, Available-for-Sale, Estimated Fair Value
Due in one year or less	37,155
Due after one year through five years	749,870
Due after five years through ten years	975,553
Due after ten years	2,246,853
Securities available‑for‑sale	$ 4,009,431	$ 3,774,431