Investment Securities (Details 2) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Amortized Cost
Due in one year or less	$ 39,300
Due after one year through five years	716,172
Due after five years through ten years	970,758
Due after ten years	2,155,497
Total securities available-for-sale	3,881,727	$ 3,721,525
Fair Value
Due in one year or less	39,272
Due after one year through five years	707,368
Due after five years through ten years	937,317
Due after ten years	2,136,376
Total securities available-for-sale	$ 3,820,333	$ 3,774,431