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Residential Mortgage Securities and MSR-Related Assets (Narrative) (Details) - USD ($) | 3 Months Ended
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Mar. 31, 2020 | Mar. 31, 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 | $ 419,651,000 | $ 0
Available-for-sale, unrealized loss position, accumulated loss | 89,388,000 |
Loans in Unrealized Loss Position |  |
Debt Securities, Available-for-sale [Line Items] |  |
Impairment and other losses on securities available-for-sale and other assets | (63,500,000) |
Agency MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Available-for-sale, unrealized loss position, accumulated loss | 0 |
Non-Agency MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Available-for-sale, unrealized loss position, accumulated loss | $ 21,643,000 |
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 Represents the minimum period of the fixed rate mortgages which act as security for mortgage backed securities in the entity's portfolio. + References No definition available. + Details
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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=118939692&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=118955579&loc=SL82922888-210455 + Details
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