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Mortgage-Backed Securities - Investment Type (Details) - USD ($) $ in Thousands | Jun. 30, 2024 | Dec. 31, 2023
--- | --- | ---
Debt Securities, Trading and Available-for-sale [Abstract] |  |  |
Par Value |  | $ 6,456,137 | $ 6,143,945
Amortized Cost |  | 6,568,580 | 6,283,185
Non-Agency other, Amortized Cost |  | 1,067,477 | 1,131,769
Fair Value |  | 6,193,139 | 6,038,948
Gross Unrealized Gain |  | 1,359 | 1,324
Gross Unrealized Loss |  | (178,914) | (159,826)
Fair Value |  | 889,922 | 973,267
Amortized Cost |  | 5,501,103 | 5,151,416
Gross Unrealized Gain |  | 13,333 | 48,461
Gross Unrealized Loss |  | (211,219) | (134,196)
Fair Value |  | 5,303,217 | 5,065,681
Residential Mortgage Backed Securities [Member] | Agency MBS |  |  |
Debt Securities, Trading and Available-for-sale [Abstract] |  |  |
Par Value |  | 6,353,838 | 6,022,502
Amortized Cost |  | 6,326,070 | 5,993,922
Non-Agency other, Amortized Cost |  | 863,181 | 898,420
Fair Value |  | 5,962,418 | 5,763,532
Gross Unrealized Gain |  | 0 | 0
Gross Unrealized Loss |  | (168,488) | (148,606)
Fair Value |  | 694,693 | 749,814
Amortized Cost |  | 5,462,889 | 5,095,502
Gross Unrealized Gain |  | 13,333 | 48,459
Gross Unrealized Loss |  | (208,497) | (130,243)
Fair Value |  | 5,267,725 | 5,013,718
Commercial Mortgage Backed Securities [Member] | Agency MBS |  |  |
Debt Securities, Trading and Available-for-sale [Abstract] |  |  |
Par Value |  | 102,299 | 121,293
Amortized Cost |  | 102,516 | 121,799
Non-Agency other, Amortized Cost |  | 102,516 | 106,527
Fair Value |  | 97,482 | 115,595
Gross Unrealized Gain |  | 0 | 28
Gross Unrealized Loss |  | (5,034) | (5,159)
Fair Value |  | 97,482 | 101,396
Amortized Cost |  |  | 15,272
Gross Unrealized Gain |  |  | 0
Gross Unrealized Loss |  |  | (1,073)
Fair Value |  |  | 14,199
Interest-Only-Strip [Member] |  |  |
Debt Securities, Trading and Available-for-sale [Abstract] |  |  |
Amortized Cost | [1] | 139,994 | 167,314
Non-Agency other, Amortized Cost |  | 101,780 | 126,672
Fair Value | [1] | 133,239 | 159,718
Gross Unrealized Gain |  | 1,359 | 1,296
Gross Unrealized Loss |  | (5,392) | (6,014)
Fair Value |  | 97,747 | 121,954
Amortized Cost |  | 38,214 | 40,642
Gross Unrealized Gain |  | 0 | 2
Gross Unrealized Loss |  | (2,722) | (2,880)
Fair Value |  | 35,492 | 37,764
Interest-Only-Strip, Agency CMBS [Member] |  |  |
Debt Securities, Trading and Available-for-sale [Abstract] |  |  |
Par Value |  | 7,321,369 | 7,723,379
Interest-Only-Strip, Non-Agency CMBS [Member] |  |  |
Debt Securities, Trading and Available-for-sale [Abstract] |  |  |
Par Value |  | 3,167,395 | 3,860,007
Non-Agency MBS |  |  |
Debt Securities, Trading and Available-for-sale [Abstract] |  |  |
Par Value |  | 0 | 150
Non-Agency other, Amortized Cost |  | 0 | 150
Gross Unrealized Gain |  |  | 0
Gross Unrealized Loss |  |  | (47)
Fair Value |  | $ 0 | $ 103
[1] | (1) The notional balance for Agency CMBS IO and non-Agency CMBS IO was $7,321,369 and $3,167,395, respectively, as of June 30, 2024, and $7,723,379 and $3,860,007, respectively, as of December 31, 2023.

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