Securities - Schedule of Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Amortized Cost
Within One Year	$ 4
Over one to five years	1,987
Over five to ten years	37,630
Over ten years	242,579
Total securities	282,200
Estimated Fair Value
Within One Year	4
Over one to five years	1,995
Over five to ten years	36,737
Over ten years	241,309
Total securities	280,045
Amortized Cost
Within One Year	39,987
Over one to five years	17,797
Over five to ten years	383,303
Over ten years	2,299,045
Total held-to-maturity securities	2,740,132	$ 2,296,799
Estimated Fair Value
Within One Year	39,989
Over one to five years	17,848
Over five to ten years	368,091
Over ten years	2,264,618
Total securities	$ 2,690,546	$ 2,286,092