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INVESTMENTS - Debt Securities Held-to-Maturity (Details) - USD ($) $ in Millions | Sep. 30, 2025 | Jun. 30, 2025 | Dec. 31, 2024 | Sep. 30, 2024 | Jun. 30, 2024 | Dec. 31, 2023
--- | --- | --- | --- | --- | --- | ---
Held-to-maturity (HTM) debt securities |  |  |  |  |  |
Amortized cost, net | $ 197,092 |  | $ 242,382 |  |  |
Gross unrealized gains | 165 |  | 133 |  |  |
Gross unrealized losses | 11,911 |  | 18,105 |  |  |
Fair value | 185,346 |  | 224,410 |  |  |
Allowance for credit losses on HTM debt securities | 131 | $ 136 | 137 | $ 141 | $ 99 | $ 95
Mortgage-backed securities |  |  |  |  |  |
Held-to-maturity (HTM) debt securities |  |  |  |  |  |
Amortized cost, net | 68,576 |  | 73,789 |  |  |
Gross unrealized gains | 25 |  | 12 |  |  |
Gross unrealized losses | 7,566 |  | 10,442 |  |  |
Fair value | 61,035 |  | 63,359 |  |  |
U.S. government-sponsored agency guaranteed |  |  |  |  |  |
Held-to-maturity (HTM) debt securities |  |  |  |  |  |
Amortized cost, net | 67,355 |  | 72,542 |  |  |
Gross unrealized gains | 2 |  | 0 |  |  |
Gross unrealized losses | 7,449 |  | 10,291 |  |  |
Fair value | 59,908 |  | 62,251 |  |  |
Mortgage-backed securities - Non-U.S. residential |  |  |  |  |  |
Held-to-maturity (HTM) debt securities |  |  |  |  |  |
Amortized cost, net | 0 |  | 0 |  |  |
Gross unrealized gains | 0 |  | 0 |  |  |
Gross unrealized losses | 0 |  | 0 |  |  |
Fair value | 0 |  | 0 |  |  |
Commercial |  |  |  |  |  |
Held-to-maturity (HTM) debt securities |  |  |  |  |  |
Amortized cost, net | 1,221 |  | 1,247 |  |  |
Gross unrealized gains | 23 |  | 12 |  |  |
Gross unrealized losses | 117 |  | 151 |  |  |
Fair value | 1,127 |  | 1,108 |  |  |
U.S. treasury securities |  |  |  |  |  |
Held-to-maturity (HTM) debt securities |  |  |  |  |  |
Amortized cost, net | 92,790 |  | 126,142 |  |  |
Gross unrealized gains | 0 |  | 0 |  |  |
Gross unrealized losses | 3,738 |  | 6,934 |  |  |
Fair value | 89,052 |  | 119,208 |  |  |
State and municipal |  |  |  |  |  |
Held-to-maturity (HTM) debt securities |  |  |  |  |  |
Amortized cost, net | 8,651 |  | 8,903 |  |  |
Gross unrealized gains | 29 |  | 27 |  |  |
Gross unrealized losses | 568 |  | 668 |  |  |
Fair value | 8,112 |  | 8,262 |  |  |
Foreign government |  |  |  |  |  |
Held-to-maturity (HTM) debt securities |  |  |  |  |  |
Amortized cost, net | 771 |  | 988 |  |  |
Gross unrealized gains | 23 |  | 3 |  |  |
Gross unrealized losses | 0 |  | 0 |  |  |
Fair value | 794 |  | 991 |  |  |
Asset-backed securities |  |  |  |  |  |
Held-to-maturity (HTM) debt securities |  |  |  |  |  |
Amortized cost, net | 26,304 |  | 32,560 |  |  |
Gross unrealized gains | 88 |  | 91 |  |  |
Gross unrealized losses | 39 |  | 61 |  |  |
Fair value | $ 26,353 |  | $ 32,590 |  |  |

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