Investment Securities - Contractual Maturities of Debt Securities Available for Sale (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Amortized Cost
Due in one year	$ 6,769
Due after one year through five years	84,534
Due after five years through ten years	79,866
Due after ten years	51,528
Residential mortgage-backed securities	823,040
Amortized Cost	1,045,737	$ 1,293,506
Fair Value
Due in one year	6,824
Due after one year through five years	86,491
Due after five years through ten years	82,581
Due after ten years	53,326
Residential mortgage-backed securities	846,316
Total	$ 1,075,538	$ 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), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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