Investment Securities - Contractual Maturities of Debt Securities Available for Sale (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Amortized Cost
Due in one year	$ 26,643
Due after one year through five years	97,248
Due after five years through ten years	104,076
Due after ten years	72,696
Residential mortgage-backed securities	1,340,614
Amortized Cost	1,641,277	$ 1,558,787
Fair Value
Due in one year	26,742
Due after one year through five years	99,501
Due after five years through ten years	106,154
Due after ten years	74,265
Residential mortgage-backed securities	1,382,726
Total investment securities available for sale	$ 1,689,388	$ 1,566,801

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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