Investment Securities - Contractual Maturities of Debt Securities Held to Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Amortized Cost
Due in one year	$ 27,218
Due after one year through five years	247,844
Due after five years through ten years	129,112
Due after ten years	202,738
Residential mortgage-backed securities	1,926,900
Amortized Cost	2,533,812	$ 2,173,011
Fair Value
Due in one year	27,365
Due after one year through five years	257,620
Due after five years through ten years	130,979
Due after ten years	201,947
Residential mortgage-backed securities	1,938,608
Total	$ 2,556,519	$ 2,227,612

Amount, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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