INVESTMENT AND MORTGAGE-BACKED SECURITIES, Amortized Cost and Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Available for sale, Amortized Cost
Within one year	$ 949
One to five years	174,565
Five to ten years	212,080
Beyond ten years	7,933
Pass-through MBS issued by GSEs and Agency CMO	855,435
Amortized Cost	1,250,962	$ 520,261
Available for sale, Fair Value
Within one year	958
One to five years	174,660
Five to ten years	215,115
Beyond ten years	7,816
Pass-through MBS issued by GSEs and Agency CMO	863,239
Total	$ 1,261,788	$ 538,861

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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