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Investment Securities - Securities in Gross Unrealized Loss Position (Details) $ in Millions | Dec. 31, 2023 USD ($) security | Dec. 31, 2022 USD ($) security
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | $ 5,068 | $ 30,629
Gross Unrealized Loss - Less than 12 Months | (50) | (2,141)
Fair Value - 12 Months or Longer | 62,711 | 40,544
Gross Unrealized Loss - 12 Months or Longer | (9,102) | (8,133)
Fair Value - Total | 67,779 | 71,173
Gross Unrealized Loss - Total | $ (9,152) | $ (10,274)
Number of securities in gross unrealized loss positions | security | 2,740 | 2,840
U.S. Treasury securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | $ 733 | $ 2,464
Gross Unrealized Loss - Less than 12 Months | 0 | (57)
Fair Value - 12 Months or Longer | 2,242 | 448
Gross Unrealized Loss - 12 Months or Longer | (49) | (33)
Fair Value - Total | 2,975 | 2,912
Gross Unrealized Loss - Total | (49) | (90)
RMBS, Agency |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 3,511 | 23,271
Gross Unrealized Loss - Less than 12 Months | (43) | (1,809)
Fair Value - 12 Months or Longer | 53,987 | 36,803
Gross Unrealized Loss - 12 Months or Longer | (8,407) | (7,604)
Fair Value - Total | 57,498 | 60,074
Gross Unrealized Loss - Total | (8,450) | (9,413)
RMBS, Non-agency |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 1 | 14
Gross Unrealized Loss - Less than 12 Months | 0 | (1)
Fair Value - 12 Months or Longer | 13 | 3
Gross Unrealized Loss - 12 Months or Longer | (1) | 0
Fair Value - Total | 14 | 17
Gross Unrealized Loss - Total | (1) | (1)
Total RMBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 3,512 | 23,285
Gross Unrealized Loss - Less than 12 Months | (43) | (1,810)
Fair Value - 12 Months or Longer | 54,000 | 36,806
Gross Unrealized Loss - 12 Months or Longer | (8,408) | (7,604)
Fair Value - Total | 57,512 | 60,091
Gross Unrealized Loss - Total | (8,451) | (9,414)
Agency CMBS |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 547 | 4,325
Gross Unrealized Loss - Less than 12 Months | (7) | (267)
Fair Value - 12 Months or Longer | 6,465 | 3,214
Gross Unrealized Loss - 12 Months or Longer | (645) | (493)
Fair Value - Total | 7,012 | 7,539
Gross Unrealized Loss - Total | (652) | (760)
Other securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value - Less than 12 Months | 276 | 555
Gross Unrealized Loss - Less than 12 Months | 0 | (7)
Fair Value - 12 Months or Longer | 4 | 76
Gross Unrealized Loss - 12 Months or Longer | 0 | (3)
Fair Value - Total | 280 | 631
Gross Unrealized Loss - Total | $ 0 | $ (10)

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