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Investment Securities - Securities in Gross Unrealized Loss Position (Details) $ in Millions | Mar. 31, 2024 USD ($) security | Dec. 31, 2023 USD ($) security
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | $ 4,603 | $ 5,068
Gross Unrealized Loss - Less than 12 Months | (42) | (50)
Fair Value - 12 Months or Longer | 62,633 | 62,711
Gross Unrealized Loss - 12 Months or Longer | (10,197) | (9,102)
Fair Value - Total | 67,236 | 67,779
Gross Unrealized Loss - Total | $ (10,239) | $ (9,152)
Number of securities in gross unrealized loss positions | security | 2,770 | 2,740
U.S. Treasury securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | $ 443 | $ 733
Gross Unrealized Loss - Less than 12 Months | (1) | 0
Fair Value - 12 Months or Longer | 2,099 | 2,242
Gross Unrealized Loss - 12 Months or Longer | (38) | (49)
Fair Value - Total | 2,542 | 2,975
Gross Unrealized Loss - Total | (39) | (49)
RMBS, Agency |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 3,213 | 3,511
Gross Unrealized Loss - Less than 12 Months | (36) | (43)
Fair Value - 12 Months or Longer | 53,912 | 53,987
Gross Unrealized Loss - 12 Months or Longer | (9,470) | (8,407)
Fair Value - Total | 57,125 | 57,498
Gross Unrealized Loss - Total | (9,506) | (8,450)
RMBS, Non-agency |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 5 | 1
Gross Unrealized Loss - Less than 12 Months | 0 | 0
Fair Value - 12 Months or Longer | 14 | 13
Gross Unrealized Loss - 12 Months or Longer | (1) | (1)
Fair Value - Total | 19 | 14
Gross Unrealized Loss - Total | (1) | (1)
Total RMBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 3,218 | 3,512
Gross Unrealized Loss - Less than 12 Months | (36) | (43)
Fair Value - 12 Months or Longer | 53,926 | 54,000
Gross Unrealized Loss - 12 Months or Longer | (9,471) | (8,408)
Fair Value - Total | 57,144 | 57,512
Gross Unrealized Loss - Total | (9,507) | (8,451)
Agency CMBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 544 | 547
Gross Unrealized Loss - Less than 12 Months | (5) | (7)
Fair Value - 12 Months or Longer | 6,509 | 6,465
Gross Unrealized Loss - 12 Months or Longer | (688) | (645)
Fair Value - Total | 7,053 | 7,012
Gross Unrealized Loss - Total | (693) | (652)
Other securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 398 | 276
Gross Unrealized Loss - Less than 12 Months | 0 | 0
Fair Value - 12 Months or Longer | 99 | 4
Gross Unrealized Loss - 12 Months or Longer | 0 | 0
Fair Value - Total | 497 | 280
Gross Unrealized Loss - Total | $ 0 | $ 0

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