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Residential Mortgage Securities and MSR-Related Assets (Narrative) (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Minimum term of fixed rate mortgages underlying MBS |  |  | 15 years |
Maximum term of fixed rate mortgages underlying MBS |  |  | 30 years |
Impairment and other losses on securities available-for-sale and other assets | $ (221) | $ 0 | $ (424,966) | $ 0
Available-for-sale, unrealized loss position, accumulated loss | 6,092 |  | 6,092 |
Loans in Unrealized Loss Position |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Impairment and other losses on securities available-for-sale and other assets |  |  | (63,500) |
Non-Agency MBS |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Available-for-sale, unrealized loss position, accumulated loss | $ 3,000 |  | $ 3,000 |
Minimum | RPL/NPL MBS |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Debt instrument, basis spread on variable rate |  |  | 3.00% |
Debt instrument, coupon step-up period |  |  | 36 months |
Maximum | RPL/NPL MBS |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |
Debt instrument, basis spread on variable rate |  |  | 4.00% |
Debt instrument, coupon step-up period |  |  | 48 months |

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- Definition Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27290-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 4 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922888-210455 + Details
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