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Residential Mortgage Securities and MSR Related Assets (Unrealized Losses on Residential Mortgage Securities) (Details) | Dec. 31, 2019 USD ($) security | Dec. 31, 2018 USD ($)
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Fair value, less than 12 months | $ 59,108,000 |
Unrealized losses, less than 12 months | $ 343,000 |
Number of securities, less than 12 months | security | 45 |
Fair value, 12 months or more | $ 792,787,000 |
Unrealized losses, 12 months or more | $ 18,475,000 |
Number of securities, 12 months or more | security | 385 |
Fair Value | $ 851,895,000 |
Unrealized losses | 18,818,000 |
MBS and CRT securities | 3,983,519,000 | $ 6,509,333,000
Unrealized losses | 18,818,000 | 63,783,000
Agency MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair value, less than 12 months | 59,108,000 |
Unrealized losses, less than 12 months | $ 343,000 |
Number of securities, less than 12 months | security | 45 |
Fair value, 12 months or more | $ 760,049,000 |
Unrealized losses, 12 months or more | $ 18,366,000 |
Number of securities, 12 months or more | security | 376 |
Fair Value | $ 819,157,000 |
Unrealized losses | 18,709,000 |
MBS and CRT securities | 1,664,582,000 | 2,698,213,000
Unrealized losses | 18,709,000 | 49,498,000
Non-Agency MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair value, less than 12 months | 0 |
Unrealized losses, less than 12 months | $ 0 |
Number of securities, less than 12 months | security | 0 |
Fair value, 12 months or more | $ 7,734,000 |
Unrealized losses, 12 months or more | $ 18,000 |
Number of securities, 12 months or more | security | 2 |
Fair Value | $ 7,734,000 |
Unrealized losses | 18,000 |
MBS and CRT securities | 2,063,529,000 | 3,318,299,000
Unrealized losses | 18,000 | 8,389,000
Expected to Recover Par |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair value, less than 12 months | 0 |
Unrealized losses, less than 12 months | $ 0 |
Number of securities, less than 12 months | security | 0 |
Fair value, 12 months or more | $ 7,492,000 |
Unrealized losses, 12 months or more | $ 9,000 |
Number of securities, 12 months or more | security | 1 |
Fair Value | $ 7,492,000 |
Unrealized losses | 9,000 |
MBS and CRT securities | 725,668,000 | 1,527,700,000
Unrealized losses | 9,000 | 7,620,000
Expected to Recover Less Than Par |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair value, less than 12 months | 0 |
Unrealized losses, less than 12 months | $ 0 |
Number of securities, less than 12 months | security | 0 |
Fair value, 12 months or more | $ 242,000 |
Unrealized losses, 12 months or more | $ 9,000 |
Number of securities, 12 months or more | security | 1 |
Fair Value | $ 242,000 |
Unrealized losses | 9,000 |
MBS and CRT securities | 1,337,861,000 | 1,790,599,000
Unrealized losses | 9,000 | 769,000
Total MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair value, less than 12 months | 59,108,000 |
Unrealized losses, less than 12 months | $ 343,000 |
Number of securities, less than 12 months | security | 45 |
Fair value, 12 months or more | $ 767,783,000 |
Unrealized losses, 12 months or more | $ 18,384,000 |
Number of securities, 12 months or more | security | 378 |
Fair Value | $ 826,891,000 |
Unrealized losses | 18,727,000 |
MBS and CRT securities | 3,728,111,000 | 6,016,512,000
Unrealized losses | 18,727,000 | 57,887,000
CRT securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair value, less than 12 months | 0 |
Unrealized losses, less than 12 months | $ 0 |
Number of securities, less than 12 months | security | 0 |
Fair value, 12 months or more | $ 25,004,000 |
Unrealized losses, 12 months or more | $ 91,000 |
Number of securities, 12 months or more | security | 7 |
Fair Value | $ 25,004,000 |
Unrealized losses | 91,000 |
MBS and CRT securities | 255,408,000 | 492,821,000
Unrealized losses | 91,000 | 5,896,000
Agency MBS, Fair Value Option |  |
Debt Securities, Available-for-sale [Line Items] |  |
Unrealized losses | 0 | 3,300,000
CRT in Loss Positions Only, Fair Value Option |  |
Debt Securities, Available-for-sale [Line Items] |  |
MBS and CRT securities | 25,000,000.0 |
Unrealized losses | 91,000 |
Fannie Mae | Agency MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair value, less than 12 months | 57,884,000 |
Unrealized losses, less than 12 months | $ 341,000 |
Number of securities, less than 12 months | security | 44 |
Fair value, 12 months or more | $ 605,765,000 |
Unrealized losses, 12 months or more | $ 14,400,000 |
Number of securities, 12 months or more | security | 275 |
Fair Value | $ 663,649,000 |
Unrealized losses | 14,741,000 |
MBS and CRT securities | 1,157,993,000 | 1,762,032,000
Unrealized losses | 14,741,000 | 32,321,000
Freddie Mac | Agency MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair value, less than 12 months | 1,224,000 |
Unrealized losses, less than 12 months | $ 2,000 |
Number of securities, less than 12 months | security | 1 |
Fair value, 12 months or more | $ 154,284,000 |
Unrealized losses, 12 months or more | $ 3,966,000 |
Number of securities, 12 months or more | security | 101 |
Fair Value | $ 155,508,000 |
Unrealized losses | 3,968,000 |
MBS and CRT securities | 502,468,000 | 931,318,000
Unrealized losses | $ 3,968,000 | $ 17,177,000

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