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Securities, at Fair Value (Impact of AFS Securities on AOCI) (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020
AOCI from AFS Securities: |  |  |  |
Unrealized gain on AFS securities at beginning of period | $ 75,752 | $ 148,910 | $ 79,607 | $ 392,722
Unrealized (loss)/gain on AFS securities, net | (9,589) | 48,715 | (13,444) | 393,503
Reclassification adjustment for MBS sales included in net income | 0 | (144,736) | 0 | (389,067)
Reclassification adjustment for impairment included in net income | 0 | 0 | 0 | (344,269)
Change in AOCI from AFS securities | (9,589) | (96,021) | (13,444) | (339,833)
Balance at end of period | 66,163 | 52,889 | 66,163 | 52,889
Agency MBS |  |  |  |
AOCI from AFS Securities: |  |  |  |
Unrealized (loss)/gain on AFS securities, net | $ (9,589) | $ 48,715 | $ (13,444) | $ 393,503

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