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Residential Mortgage Securities and MSR Related Assets (MBS and CRT Securities) (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | $ 4,044,818,000 | $ 6,646,178,000
Purchase Premiums | 67,108,000 | 112,369,000
Accretable Purchase Discounts | (90,694,000) | (154,942,000)
Discount Designated as Credit Reserve and OTTI | (436,598,000) | (516,116,000)
Amortized Cost | 3,585,248,000 | 6,088,525,000
Fair Value | 3,983,519,000 | 6,509,333,000
Gross Unrealized Gains | 417,089,000 | 484,591,000
Gross Unrealized Losses | (18,818,000) | (63,783,000)
Net Unrealized Gain/(Loss) | 398,271,000 | 420,808,000
Principal payments receivable | 614,000 | 1,000,000.0
Agency MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 1,604,583,000 | 2,630,630,000
Purchase Premiums | 62,790,000 | 103,008,000
Accretable Purchase Discounts | (22,000) | (24,000)
Discount Designated as Credit Reserve and OTTI | 0 | 0
Amortized Cost | 1,667,965,000 | 2,734,650,000
Fair Value | 1,664,582,000 | 2,698,213,000
Gross Unrealized Gains | 15,326,000 | 13,061,000
Gross Unrealized Losses | (18,709,000) | (49,498,000)
Net Unrealized Gain/(Loss) | (3,383,000) | (36,437,000)
Agency MBS | Fannie Mae |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 1,119,708,000 | 1,716,340,000
Purchase Premiums | 43,249,000 | 65,930,000
Accretable Purchase Discounts | (22,000) | (24,000)
Discount Designated as Credit Reserve and OTTI | 0 | 0
Amortized Cost | 1,162,935,000 | 1,782,246,000
Fair Value | 1,157,993,000 | 1,762,032,000
Gross Unrealized Gains | 9,799,000 | 12,107,000
Gross Unrealized Losses | (14,741,000) | (32,321,000)
Net Unrealized Gain/(Loss) | (4,942,000) | (20,214,000)
Agency MBS | Freddie Mac |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 480,879,000 | 909,561,000
Purchase Premiums | 19,468,000 | 36,991,000
Accretable Purchase Discounts | 0 | 0
Discount Designated as Credit Reserve and OTTI | 0 | 0
Amortized Cost | 500,961,000 | 947,588,000
Fair Value | 502,468,000 | 931,318,000
Gross Unrealized Gains | 5,475,000 | 907,000
Gross Unrealized Losses | (3,968,000) | (17,177,000)
Net Unrealized Gain/(Loss) | 1,507,000 | (16,270,000)
Agency MBS | Ginnie Mae |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 3,996,000 | 4,729,000
Purchase Premiums | 73,000 | 87,000
Accretable Purchase Discounts | 0 | 0
Discount Designated as Credit Reserve and OTTI | 0 | 0
Amortized Cost | 4,069,000 | 4,816,000
Fair Value | 4,121,000 | 4,863,000
Gross Unrealized Gains | 52,000 | 47,000
Gross Unrealized Losses | 0 | 0
Net Unrealized Gain/(Loss) | 52,000 | 47,000
Non-Agency MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 2,195,303,000 | 3,538,804,000
Purchase Premiums | 0 | 40,000
Accretable Purchase Discounts | (90,617,000) | (155,025,000)
Discount Designated as Credit Reserve and OTTI | (436,598,000) | (516,116,000)
Amortized Cost | 1,668,088,000 | 2,867,703,000
Fair Value | 2,063,529,000 | 3,318,299,000
Gross Unrealized Gains | 395,459,000 | 458,985,000
Gross Unrealized Losses | (18,000) | (8,389,000)
Net Unrealized Gain/(Loss) | 395,441,000 | 450,596,000
Credit reserve | 426,000,000.0 | 503,300,000
OTTI | 10,600,000 | 12,800,000
Expected to Recover Par |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 722,477,000 | 1,536,485,000
Purchase Premiums | 0 | 40,000
Accretable Purchase Discounts | (16,661,000) | (21,725,000)
Discount Designated as Credit Reserve and OTTI | 0 | 0
Amortized Cost | 705,816,000 | 1,514,800,000
Fair Value | 725,668,000 | 1,527,700,000
Gross Unrealized Gains | 19,861,000 | 20,520,000
Gross Unrealized Losses | (9,000) | (7,620,000)
Net Unrealized Gain/(Loss) | 19,852,000 | 12,900,000
Expected to Recover Less Than Par |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 1,472,826,000 | 2,002,319,000
Purchase Premiums | 0 | 0
Accretable Purchase Discounts | (73,956,000) | (133,300,000)
Discount Designated as Credit Reserve and OTTI | (436,598,000) | (516,116,000)
Amortized Cost | 962,272,000 | 1,352,903,000
Fair Value | 1,337,861,000 | 1,790,599,000
Gross Unrealized Gains | 375,598,000 | 438,465,000
Gross Unrealized Losses | (9,000) | (769,000)
Net Unrealized Gain/(Loss) | $ 375,589,000 | $ 437,696,000
Percentage of current face amount of Non-Agency MBS to be recovered | 80.00% | 85.00%
Total MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | $ 3,799,886,000 | $ 6,169,434,000
Purchase Premiums | 62,790,000 | 103,048,000
Accretable Purchase Discounts | (90,639,000) | (155,049,000)
Discount Designated as Credit Reserve and OTTI | (436,598,000) | (516,116,000)
Amortized Cost | 3,336,053,000 | 5,602,353,000
Fair Value | 3,728,111,000 | 6,016,512,000
Gross Unrealized Gains | 410,785,000 | 472,046,000
Gross Unrealized Losses | (18,727,000) | (57,887,000)
Net Unrealized Gain/(Loss) | 392,058,000 | 414,159,000
CRT securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 244,932,000 | 476,744,000
Purchase Premiums | 4,318,000 | 9,321,000
Accretable Purchase Discounts | (55,000) | 107,000
Discount Designated as Credit Reserve and OTTI | 0 | 0
Amortized Cost | 249,195,000 | 486,172,000
Fair Value | 255,408,000 | 492,821,000
Gross Unrealized Gains | 6,304,000 | 12,545,000
Gross Unrealized Losses | (91,000) | (5,896,000)
Net Unrealized Gain/(Loss) | 6,213,000 | 6,649,000
Agency MBS, Fair Value Option |  |
Debt Securities, Available-for-sale [Line Items] |  |
Gross Unrealized Gains | 4,500,000 | 0
Gross Unrealized Losses | 0 | (3,300,000)
Debt securities, fair value option | 280,300,000 | 736,500,000
RPL/NPL MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 632,300,000 | 1,400,000,000
Amortized Cost | 631,800,000 | 1,400,000,000
Fair Value | 635,000,000.0 | 1,400,000,000
CRT, Fair Value Option |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value | 255,400,000 | 477,400,000
Gross Unrealized Gains | 6,300,000 | 12,500,000
Gross Unrealized Losses | $ (91,000) | $ (5,600,000)

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