Investment Securities - Contractual Maturities of Investment Securities Available for Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Amortized Cost
Due in one year	$ 14,553
Due after one year through five years	82,656
Due after five years through ten years	92,674
Due after ten years	53,254
Residential mortgage-backed securities	1,050,369
Amortized Cost	1,293,506	$ 1,558,787
Fair Value
Due in one year	14,555
Due after one year through five years	85,179
Due after five years through ten years	94,629
Due after ten years	55,088
Residential mortgage-backed securities	1,090,022
Fair Value	$ 1,339,473	$ 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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