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Residential Mortgage Securities and MSR-Related Assets (Residential and Mortgage Securities) (Details) - USD ($) | Mar. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | $ 2,354,515,000 | $ 4,044,818,000
Purchase Premiums | 22,184,000 | 67,108,000
Accretable Purchase Discounts | (91,028,000) | (90,694,000)
Discount Designated as Credit Reserve and OTTI | (441,477,000) | (436,598,000)
Amortized Cost | 1,844,710,000 | 3,585,248,000
Gross Unrealized Gains | 172,132,000 | 417,089,000
Gross Unrealized Losses | (89,388,000) | (18,818,000)
Net Unrealized Gain/(Loss) | 82,744,000 | 398,271,000
Fair Value | 1,927,454,000 | 3,983,519,000
Principal payments receivable | 516,000 | 614,000
Agency MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 532,905,000 | 1,604,583,000
Purchase Premiums | 18,921,000 | 62,790,000
Accretable Purchase Discounts | (18,000) | (22,000)
Discount Designated as Credit Reserve and OTTI | (4,868,000) | 0
Amortized Cost | 547,456,000 | 1,667,965,000
Gross Unrealized Gains | 5,957,000 | 15,326,000
Gross Unrealized Losses | 0 | (18,709,000)
Net Unrealized Gain/(Loss) | 5,957,000 | (3,383,000)
Fair Value | 553,413,000 | 1,664,582,000
Agency MBS | Fannie Mae |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 433,397,000 | 1,119,708,000
Purchase Premiums | 15,384,000 | 43,249,000
Accretable Purchase Discounts | (18,000) | (22,000)
Discount Designated as Credit Reserve and OTTI | (4,747,000) | 0
Amortized Cost | 444,016,000 | 1,162,935,000
Gross Unrealized Gains | 4,242,000 | 9,799,000
Gross Unrealized Losses | 0 | (14,741,000)
Net Unrealized Gain/(Loss) | 4,242,000 | (4,942,000)
Fair Value | 448,258,000 | 1,157,993,000
Agency MBS | Freddie Mac |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 95,759,000 | 480,879,000
Purchase Premiums | 3,468,000 | 19,468,000
Accretable Purchase Discounts | 0 | 0
Discount Designated as Credit Reserve and OTTI | (121,000) | 0
Amortized Cost | 99,622,000 | 500,961,000
Gross Unrealized Gains | 1,655,000 | 5,475,000
Gross Unrealized Losses | 0 | (3,968,000)
Net Unrealized Gain/(Loss) | 1,655,000 | 1,507,000
Fair Value | 101,277,000 | 502,468,000
Agency MBS | Ginnie Mae |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 3,749,000 | 3,996,000
Purchase Premiums | 69,000 | 73,000
Accretable Purchase Discounts | 0 | 0
Discount Designated as Credit Reserve and OTTI | 0 | 0
Amortized Cost | 3,818,000 | 4,069,000
Gross Unrealized Gains | 60,000 | 52,000
Gross Unrealized Losses | 0 | 0
Net Unrealized Gain/(Loss) | 60,000 | 52,000
Fair Value | 3,878,000 | 4,121,000
Non-Agency MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 1,455,848,000 | 2,195,303,000
Purchase Premiums | 0 | 0
Accretable Purchase Discounts | (90,968,000) | (90,617,000)
Discount Designated as Credit Reserve and OTTI | (389,472,000) | (436,598,000)
Amortized Cost | 975,408,000 | 1,668,088,000
Gross Unrealized Gains | 166,175,000 | 395,459,000
Gross Unrealized Losses | (21,643,000) | (18,000)
Net Unrealized Gain/(Loss) | 144,532,000 | 395,441,000
Fair Value | 1,119,940,000 | 2,063,529,000
Expected to Recover Par |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 150,181,000 | 722,477,000
Purchase Premiums | 0 | 0
Accretable Purchase Discounts | (13,191,000) | (16,661,000)
Discount Designated as Credit Reserve and OTTI | 0 | 0
Amortized Cost | 136,990,000 | 705,816,000
Gross Unrealized Gains | 6,175,000 | 19,861,000
Gross Unrealized Losses | (21,643,000) | (9,000)
Net Unrealized Gain/(Loss) | (15,468,000) | 19,852,000
Fair Value | 121,522,000 | 725,668,000
Expected to Recover Less Than Par |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 1,305,667,000 | 1,472,826,000
Purchase Premiums | 0 | 0
Accretable Purchase Discounts | (77,777,000) | (73,956,000)
Discount Designated as Credit Reserve and OTTI | (389,472,000) | (436,598,000)
Amortized Cost | 838,418,000 | 962,272,000
Gross Unrealized Gains | 160,000,000 | 375,598,000
Gross Unrealized Losses | 0 | (9,000)
Net Unrealized Gain/(Loss) | 160,000,000 | 375,589,000
Fair Value | $ 998,418,000 | $ 1,337,861,000
Percentage of current face amount of Non-Agency MBS to be recovered | 73.00% | 80.00%
Total MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | $ 1,988,753,000 | $ 3,799,886,000
Purchase Premiums | 18,921,000 | 62,790,000
Accretable Purchase Discounts | (90,986,000) | (90,639,000)
Discount Designated as Credit Reserve and OTTI | (394,340,000) | (436,598,000)
Amortized Cost | 1,522,864,000 | 3,336,053,000
Gross Unrealized Gains | 172,132,000 | 410,785,000
Gross Unrealized Losses | (21,643,000) | (18,727,000)
Net Unrealized Gain/(Loss) | 150,489,000 | 392,058,000
Fair Value | 1,673,353,000 | 3,728,111,000
CRT securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 365,762,000 | 244,932,000
Purchase Premiums | 3,263,000 | 4,318,000
Accretable Purchase Discounts | (42,000) | (55,000)
Discount Designated as Credit Reserve and OTTI | (47,137,000) | 0
Amortized Cost | 321,846,000 | 249,195,000
Gross Unrealized Gains | 0 | 6,304,000
Gross Unrealized Losses | (67,745,000) | (91,000)
Net Unrealized Gain/(Loss) | (67,745,000) | 6,213,000
Fair Value | 254,101,000 | 255,408,000
Agency MBS, Fair Value Option |  |
Debt Securities, Available-for-sale [Line Items] |  |
Gross Unrealized Gains | 499,000 | 4,500,000
Gross Unrealized Losses | 0 | 0
Debt securities, fair value option | 14,500,000 | 280,300,000
RPL/NPL MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 101,400,000 | 632,300,000
Amortized Cost | 101,100,000 | 631,800,000
Fair Value | 79,500,000 | 635,000,000.0
CRT, Fair Value Option |  |
Debt Securities, Available-for-sale [Line Items] |  |
Gross Unrealized Gains | 0 | 6,300,000
Gross Unrealized Losses | (67,700,000) | (91,000)
Fair Value | $ 188,600,000 | $ 255,400,000

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