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Investment Securities - Additional Information (Detail) | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2024 USD ($) security | Jun. 30, 2023 USD ($) | Jun. 30, 2024 USD ($) security | Jun. 30, 2023 USD ($) | Dec. 31, 2023 USD ($)
Summary of Investment Holdings [Line Items] |  |  |  |  |
Gross realized gains(loss) on sale of investment securities |  | $ 13,000,000 | $ 0 | $ 0 |
Gains (losses) on equity securities | $ (8,000,000) | $ 1,000,000 | $ (6,000,000) | $ 1,000,000 |
Number of debt securities with aggregate gross unrealized losses | security | 3,996 |  | 3,996 |  |
Unrealized losses on individual debt securities |  |  | $ (1,500,000,000) |  |
Cost method equity securities | $ 929,000,000 |  | 929,000,000 |  |
Allowance for credit losses | 0 |  | 0 |  | $ 0
Investment securities pledged to secure debt carrying value | 7,100,000,000 |  | 7,100,000,000 |  | 8,200,000,000
Carrying value of investment securities pledged related to repurchase transactions | $ 311,000,000 |  | $ 311,000,000 |  | $ 393,000,000

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