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Residential Mortgage Securities and MSR-Related Assets (Impact of AFS Securities on AOCI) (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018
AOCI from AFS Securities: |  |  |  |
Unrealized gain on AFS securities at beginning of period | $ 439,898 | $ 548,551 | $ 417,167 | $ 620,648
Reclassification adjustment for MBS sales included in net income | (14,499) | (9,455) | (36,370) | (25,580)
Change in AOCI from AFS securities | (9,016) | (43,733) | 13,715 | (115,830)
Balance at end of period | 430,882 | 504,818 | 430,882 | 504,818
Agency MBS |  |  |  |
AOCI from AFS Securities: |  |  |  |
Unrealized (loss)/gain on AFS securities, net | 603 | (9,177) | 22,483 | (27,507)
Non-Agency MBS |  |  |  |
AOCI from AFS Securities: |  |  |  |
Unrealized (loss)/gain on AFS securities, net | 2,856 | (25,101) | 22,211 | (62,979)
MSR-related assets |  |  |  |
AOCI from AFS Securities: |  |  |  |
Unrealized (loss)/gain on AFS securities, net | $ 2,024 | $ 0 | $ 5,391 | $ 236

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