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Residential Mortgage Securities and MSR-Related Assets (Residential and Mortgage Securities) (Details) - USD ($) | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2019 | Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | $ 4,641,832,000 | $ 6,646,178,000
Purchase Premiums | 74,178,000 | 112,369,000
Accretable Purchase Discounts | (102,437,000) | (154,942,000)
Discount Designated as Credit Reserve and OTTI | (462,095,000) | (516,116,000)
Amortized Cost | 4,152,443,000 | 6,088,525,000
Gross Unrealized Gains | 456,885,000 | 484,591,000
Gross Unrealized Losses | (19,774,000) | (63,783,000)
Net Unrealized Gain/(Loss) | 437,111,000 | 420,808,000
Fair Value | 4,589,554,000 | 6,509,333,000
Principal payments receivable | 965,000 | 1,000,000.0
Agency MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 1,747,799,000 | 2,630,630,000
Purchase Premiums | 68,296,000 | 103,008,000
Accretable Purchase Discounts | (23,000) | (24,000)
Discount Designated as Credit Reserve and OTTI | 0 | 0
Amortized Cost | 1,817,037,000 | 2,734,650,000
Gross Unrealized Gains | 16,108,000 | 13,061,000
Gross Unrealized Losses | (19,272,000) | (49,498,000)
Net Unrealized Gain/(Loss) | (3,164,000) | (36,437,000)
Fair Value | 1,813,873,000 | 2,698,213,000
Agency MBS | Fannie Mae |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 1,217,508,000 | 1,716,340,000
Purchase Premiums | 46,917,000 | 65,930,000
Accretable Purchase Discounts | (23,000) | (24,000)
Discount Designated as Credit Reserve and OTTI | 0 | 0
Amortized Cost | 1,264,402,000 | 1,782,246,000
Gross Unrealized Gains | 10,896,000 | 12,107,000
Gross Unrealized Losses | (15,282,000) | (32,321,000)
Net Unrealized Gain/(Loss) | (4,386,000) | (20,214,000)
Fair Value | 1,260,016,000 | 1,762,032,000
Agency MBS | Freddie Mac |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 526,173,000 | 909,561,000
Purchase Premiums | 21,303,000 | 36,991,000
Accretable Purchase Discounts | 0 | 0
Discount Designated as Credit Reserve and OTTI | 0 | 0
Amortized Cost | 548,441,000 | 947,588,000
Gross Unrealized Gains | 5,159,000 | 907,000
Gross Unrealized Losses | (3,990,000) | (17,177,000)
Net Unrealized Gain/(Loss) | 1,169,000 | (16,270,000)
Fair Value | 549,610,000 | 931,318,000
Agency MBS | Ginnie Mae |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 4,118,000 | 4,729,000
Purchase Premiums | 76,000 | 87,000
Accretable Purchase Discounts | 0 | 0
Discount Designated as Credit Reserve and OTTI | 0 | 0
Amortized Cost | 4,194,000 | 4,816,000
Gross Unrealized Gains | 53,000 | 47,000
Gross Unrealized Losses | 0 | 0
Net Unrealized Gain/(Loss) | 53,000 | 47,000
Fair Value | 4,247,000 | 4,863,000
Non-Agency MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 2,529,749,000 | 3,538,804,000
Purchase Premiums | 0 | 40,000
Accretable Purchase Discounts | (102,297,000) | (155,025,000)
Discount Designated as Credit Reserve and OTTI | (462,095,000) | (516,116,000)
Amortized Cost | 1,965,357,000 | 2,867,703,000
Gross Unrealized Gains | 432,693,000 | 458,985,000
Gross Unrealized Losses | (261,000) | (8,389,000)
Net Unrealized Gain/(Loss) | 432,432,000 | 450,596,000
Fair Value | 2,397,789,000 | 3,318,299,000
Credit reserve | 451,100,000 | 503,300,000
OTTI | 11,000,000.0 | 12,800,000
Expected to Recover Par |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 917,981,000 | 1,536,485,000
Purchase Premiums | 0 | 40,000
Accretable Purchase Discounts | (14,176,000) | (21,725,000)
Discount Designated as Credit Reserve and OTTI | 0 | 0
Amortized Cost | 903,805,000 | 1,514,800,000
Gross Unrealized Gains | 17,905,000 | 20,520,000
Gross Unrealized Losses | (5,000) | (7,620,000)
Net Unrealized Gain/(Loss) | 17,900,000 | 12,900,000
Fair Value | 921,705,000 | 1,527,700,000
Expected to Recover Less Than Par |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 1,611,768,000 | 2,002,319,000
Purchase Premiums | 0 | 0
Accretable Purchase Discounts | (88,121,000) | (133,300,000)
Discount Designated as Credit Reserve and OTTI | (462,095,000) | (516,116,000)
Amortized Cost | 1,061,552,000 | 1,352,903,000
Gross Unrealized Gains | 414,788,000 | 438,465,000
Gross Unrealized Losses | (256,000) | (769,000)
Net Unrealized Gain/(Loss) | 414,532,000 | 437,696,000
Fair Value | $ 1,476,084,000 | $ 1,790,599,000
Percentage of current face amount of Non-Agency MBS to be recovered | 82.00% | 85.00%
Total MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | $ 4,277,548,000 | $ 6,169,434,000
Purchase Premiums | 68,296,000 | 103,048,000
Accretable Purchase Discounts | (102,320,000) | (155,049,000)
Discount Designated as Credit Reserve and OTTI | (462,095,000) | (516,116,000)
Amortized Cost | 3,782,394,000 | 5,602,353,000
Gross Unrealized Gains | 448,801,000 | 472,046,000
Gross Unrealized Losses | (19,533,000) | (57,887,000)
Net Unrealized Gain/(Loss) | 429,268,000 | 414,159,000
Fair Value | 4,211,662,000 | 6,016,512,000
CRT securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 364,284,000 | 476,744,000
Purchase Premiums | 5,882,000 | 9,321,000
Accretable Purchase Discounts | (117,000) | 107,000
Discount Designated as Credit Reserve and OTTI | 0 | 0
Amortized Cost | 370,049,000 | 486,172,000
Gross Unrealized Gains | 8,084,000 | 12,545,000
Gross Unrealized Losses | (241,000) | (5,896,000)
Net Unrealized Gain/(Loss) | 7,843,000 | 6,649,000
Fair Value | 377,892,000 | 492,821,000
Agency MBS, Fair Value Option |  |
Debt Securities, Available-for-sale [Line Items] |  |
Gross Unrealized Gains | 4,100,000 | 0
Gross Unrealized Losses | 0 | (3,300,000)
Debt Securities, Fair Value Option | 312,500,000 | 736,500,000
RPL/NPL MBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Principal/ Current Face | 824,800,000 | 1,400,000,000
Amortized Cost | 824,300,000 | 1,400,000,000
Fair Value | 828,100,000 | 1,400,000,000
CRT, Fair Value Option |  |
Debt Securities, Available-for-sale [Line Items] |  |
Gross Unrealized Gains | 7,800,000 | 12,500,000
Gross Unrealized Losses | (200,000) | (5,600,000)
Fair Value | $ 351,400,000 | $ 477,400,000

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