Securities (Scheduled Maturities of Investment Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Amortized Cost
Due within one year	$ 555,390
Due after one year through five years	684,781
Due after five years through ten years	248,519
Due after ten years	1,299,203
Total available-for-sale debt securities, Amortized Cost	2,787,893
Fair Value
Due within one year	519,115
Due after one year through five years	659,431
Due after five years through ten years	242,054
Due after ten years	1,255,910
Total available-for-sale investment securities	2,676,510
Fair values of available-for-sale investment securities pledged	$ 429,800	$ 534,300

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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