Investment Securities - Contractual Maturities of Debt Securities Available for Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Amortized Cost
Due in one year	$ 13,361
Due after one year through five years	77,866
Due after five years through ten years	92,143
Due after ten years	48,814
Residential mortgage-backed securities	852,398
Amortized Cost	1,084,582	$ 1,293,506
Fair Value
Due in one year	13,421
Due after one year through five years	79,806
Due after five years through ten years	94,029
Due after ten years	50,629
Residential mortgage-backed securities	878,336
Total	$ 1,116,221	$ 1,339,473

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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