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Fair Value Measurements - Carrying Amounts and Estimated Fair Value for Certain Financial Instruments (Detail) - USD ($) $ in Millions | Mar. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Financial assets: |  |
Interest-bearing deposits at banks | $ 32,144 | $ 28,069
Investment securities held to maturity | 15,078 | 15,330
Equity and other securities | 928 | 859
Loans and leases, net | 132,782 | 131,939
Financial liabilities: |  |
Noninterest-bearing deposits | 50,578 | 49,294
Savings and interest-checking deposits | 96,339 | 93,221
Time deposits | 20,279 | 20,759
Short-term borrowings | 295 | 316
Long-term borrowings | 11,450 | 8,201
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] |  |
Financial assets: |  |
Cash and cash equivalents | 1,396 | 1,668
Significant Observable Inputs (Level 2) [Member] |  |
Financial assets: |  |
Cash and cash equivalents | 299 | 63
Interest-bearing deposits at banks | 32,144 | 28,069
Investment securities held to maturity | 13,821 | 14,262
Loans and leases, net | 7,354 | 7,240
Financial liabilities: |  |
Time deposits | 20,236 | 20,715
Short-term borrowings | 4,795 | 5,316
Long-term borrowings | 11,370 | 8,107
Significant Unobservable Inputs (Level 3) [Member] |  |
Financial assets: |  |
Investment securities held to maturity | 44 | 46
Loans and leases, net | 122,417 | 121,898
Carrying Amount [Member] |  |
Financial assets: |  |
Cash and cash equivalents | 1,695 | 1,731
Interest-bearing deposits at banks | 32,144 | 28,069
Investment securities held to maturity | 15,078 | 15,330
Loans and leases, net | 132,782 | 131,939
Financial liabilities: |  |
Time deposits | 20,279 | 20,759
Short-term borrowings | 4,795 | 5,316
Long-term borrowings | 11,450 | 8,201
Cumulative Amount of Fair Value Hedging Adjustment Increasing (Decreasing) the Carrying Amount [Member] |  |
Financial assets: |  |
Cash and cash equivalents | 1,695 | 1,731
Interest-bearing deposits at banks | 32,144 | 28,069
Investment securities held to maturity | 13,865 | 14,308
Loans and leases, net | 129,771 | 129,138
Financial liabilities: |  |
Time deposits | 20,236 | 20,715
Short-term borrowings | 4,795 | 5,316
Long-term borrowings | $ 11,370 | $ 8,107

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