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Fair Value Measurements (Financial Assets and Financial Liabilities Measured at Fair Value on Recurring Basis) (Detail) - USD ($) $ in Thousands | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities available for sale, at estimated fair value | $ 16,578,371 | $ 18,243,605
Trading account securities | 31,717 | 28,045
Derivative assets: | 119,723 | 118,994
Derivative liabilities: | 41,311 | 73,829
Interest Rate Swaps Caps And Floors [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Derivative assets: | 90,715 | 86,793
Derivative liabilities: | 90,525 | 95,533
Commodity Swaps And Options [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Derivative assets: | 70,710 | 106,685
Derivative liabilities: | 69,447 | 105,392
Foreign Exchange Forward [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Derivative assets: | 22 | 11
Derivative liabilities: | 19 | 11
US Treasury Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities available for sale, at estimated fair value | 4,927,589 | 5,051,587
Trading account securities | 30,265 | 25,879
Residential Mortgage Backed Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities available for sale, at estimated fair value | 6,596,682 | 6,376,236
US States and Political Subdivisions Debt Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities available for sale, at estimated fair value | 5,011,331 | 6,773,355
Trading account securities | 1,452 | 2,166
Other Investments [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities available for sale, at estimated fair value | 42,769 | 42,427
Level 1 [Member] | Foreign Exchange Forward [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Derivative assets: | 22 | 11
Derivative liabilities: | 19 | 11
Level 1 [Member] | US Treasury Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities available for sale, at estimated fair value | 4,927,589 | 5,051,587
Trading account securities | 30,265 | 25,879
Level 2 [Member] | Interest Rate Swaps Caps And Floors [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Derivative assets: | 90,715 | 86,793
Derivative liabilities: | 90,525 | 95,533
Level 2 [Member] | Commodity Swaps And Options [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Derivative assets: | 70,710 | 106,685
Derivative liabilities: | 69,447 | 105,392
Level 2 [Member] | Residential Mortgage Backed Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities available for sale, at estimated fair value | 6,596,682 | 6,376,236
Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities available for sale, at estimated fair value | 5,011,331 | 6,773,355
Trading account securities | 1,452 | 2,166
Level 2 [Member] | Other Investments [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities available for sale, at estimated fair value | 42,769 | 42,427
US Treasury Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities available for sale, at estimated fair value | 4,927,589 | 5,051,587
Trading account securities | 30,265 | 25,879
Residential Mortgage Backed Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities available for sale, at estimated fair value | 6,596,682 | 6,376,236
US States and Political Subdivisions Debt Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities available for sale, at estimated fair value | 5,011,331 | 6,773,355
Trading account securities | 1,452 | 2,166
Other Investments [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities available for sale, at estimated fair value | $ 42,769 | $ 42,427

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