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Investment Securities (Narrative) (Details) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2026 USD ($) shares | Dec. 31, 2025 USD ($)
Debt Securities, Available-for-sale [Line Items] |  |
Percentage decrease requiring a review for impairment | 20.00% |
Fair value of securities on impairment watch list | $ 970,500,000 | $ 896,700,000
Debt Securities, Available-for-sale, Unrealized Loss Position | 6,347,485,000 | 5,882,003,000
Unrealized Loss on AFS Debt Securities | 711,443,000 | 692,094,000
AFS securities in loss position at period-end, change in unrealized loss | 19,300,000 |
Securities pledged as collateral | $ 6,700,000,000 | 7,300,000,000
Number of investments in a single issuer that exceed 10% of stockholder's equity | 0 |
No investment in a single issuer exceeds this percentage of stockholder's equity | 10.00% |
U.S. government and federal agency obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
U.S. Treasury inflation-protected securities held, at fair value | $ 380,700,000 |
Debt Securities, Available-for-sale, Unrealized Loss Position | 1,511,727,000 | 926,173,000
Unrealized Loss on AFS Debt Securities | $ 16,400,000 | $ 10,864,000
Visa Class B-2 Shares |  |
Debt Securities, Available-for-sale [Line Items] |  |
Equity Securities without Readily Determinable Fair Value, Shares | shares | 411,723 |
Equity Securities without Readily Determinable Fair Value, Carrying Value | $ 0 |
Private Equity Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair value other securities adjustments, net | $ 10,900,000 |

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