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Mortgage-Backed Securities - Investment Type (Details) - USD ($) $ in Thousands | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Debt Securities, Trading and Available-for-sale [Abstract] |  |  |
Par Value |  | $ 6,143,945 | $ 3,236,285
Amortized Cost |  | 6,283,185 | 3,522,256
Fair Value |  | 6,038,948 | 3,112,705
Amortized cost |  | 1,131,769 | 1,288,269
Gross Unrealized Gain |  | 1,324 | 507
Gross Unrealized Loss |  | (159,826) | (181,853)
Fair Value |  | 973,267 | 1,106,923
Amortized Cost |  | 5,151,416 | 2,233,987
Gross Unrealized Gain |  | 48,461 | 0
Gross Unrealized Loss |  | (134,196) | (228,205)
Fair Value |  | 5,065,681 | 2,005,782
Residential Mortgage Backed Securities [Member] | Agency MBS |  |  |
Debt Securities, Trading and Available-for-sale [Abstract] |  |  |
Par Value |  | 6,022,502 | 3,104,498
Amortized Cost |  | 5,993,922 | 3,150,873
Fair Value |  | 5,763,532 | 2,762,878
Amortized cost |  | 898,420 | 977,624
Gross Unrealized Gain |  | 0 | 0
Gross Unrealized Loss |  | (148,606) | (164,949)
Fair Value |  | 749,814 | 812,675
Amortized Cost |  | 5,095,502 | 2,173,249
Gross Unrealized Gain |  | 48,459 | 0
Gross Unrealized Loss |  | (130,243) | (223,046)
Fair Value |  | 5,013,718 | 1,950,203
Commercial Mortgage Backed Securities [Member] | Agency MBS |  |  |
Debt Securities, Trading and Available-for-sale [Abstract] |  |  |
Par Value |  | 121,293 | 131,578
Amortized Cost |  | 121,799 | 132,333
Fair Value |  | 115,595 | 124,690
Amortized cost |  | 106,527 | 117,031
Gross Unrealized Gain |  | 28 | 0
Gross Unrealized Loss |  | (5,159) | (6,474)
Fair Value |  | 101,396 | 110,557
Amortized Cost |  | 15,272 | 15,302
Gross Unrealized Gain |  | 0 | 0
Gross Unrealized Loss |  | (1,073) | (1,169)
Fair Value |  | 14,199 | 14,133
Interest-Only-Strip [Member] |  |  |
Debt Securities, Trading and Available-for-sale [Abstract] |  |  |
Amortized Cost | [1] | 167,314 | 238,841
Fair Value | [1] | 159,718 | 224,985
Amortized cost |  | 126,672 | 193,405
Gross Unrealized Gain |  | 1,296 | 507
Gross Unrealized Loss |  | (6,014) | (10,373)
Fair Value |  | 121,954 | 183,539
Amortized Cost |  | 40,642 | 45,436
Gross Unrealized Gain |  | 2 | 0
Gross Unrealized Loss |  | (2,880) | (3,990)
Fair Value |  | 37,764 | 41,446
Interest-Only-Strip, Agency CMBS [Member] |  |  |
Debt Securities, Trading and Available-for-sale [Abstract] |  |  |
Notional balance |  | 7,723,379 | 9,711,981
Interest-Only-Strip, Non-Agency CMBS [Member] |  |  |
Debt Securities, Trading and Available-for-sale [Abstract] |  |  |
Notional balance |  | 3,860,007 | 6,280,761
Non-Agency MBS |  |  |
Debt Securities, Trading and Available-for-sale [Abstract] |  |  |
Par Value |  | 150 | 209
Fair Value |  | 103 | 152
Amortized cost |  | 150 | 209
Gross Unrealized Gain |  | 0 | 0
Gross Unrealized Loss |  | (47) | (57)
Fair Value |  | $ 103 | $ 152
[1] | (1) The notional balance for Agency CMBS IO and non-Agency CMBS IO was $7,723,379 and $3,860,007, respectively, as of December 31, 2023, and $9,711,981 and $6,280,761, respectively, as of December 31, 2022.

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