Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	$ 24,509	$ 17,980
Available for sale securities	6,330,699	7,006,347
Derivative Assets, Fair Value	144,310	48,121
Derivative Liabilities, Fair Value	151,527	126,334
Securities sold not yet purchased	9,700	3,500
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	9,191	2,384
Available for sale securities	1,124,276	1,144,570
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	15,318	15,596
Available for sale securities	5,206,423	5,861,777
U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	779,375	777,070
U.S. Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	173,350	171,296
Mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	3,479,951	3,982,122
State and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	1,206,656	1,362,407
Corporates [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	344,901	367,500
Fair Value Measurement, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	24,509	17,980
Available for sale securities	6,330,699	7,006,347
Equity securities with readily determinable fair values	10,780	10,782
Company-owned life insurance	63,428	56,769
Bank-owned life insurance	520,344	510,293
Derivative Assets, Fair Value	144,310	48,121
Total	7,094,070	7,650,292
Derivative Liabilities, Fair Value	151,527	126,334
Securities sold not yet purchased	9,731	3,503
Total	161,258	129,837
Fair Value Measurement, Recurring [Member] \| Trading - other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	267	780
Fair Value Measurement, Recurring [Member] \| Collateralized loan obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	346,466	345,952
Fair Value Measurement, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	9,191	2,384
Available for sale securities	1,124,276	1,144,570
Equity securities with readily determinable fair values	10,780	10,782
Total	1,144,247	1,157,736
Fair Value Measurement, Recurring [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Trading - other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	267	780
Fair Value Measurement, Recurring [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	15,318	15,596
Available for sale securities	5,206,423	5,861,777
Company-owned life insurance	63,428	56,769
Bank-owned life insurance	520,344	510,293
Derivative Assets, Fair Value	144,310	48,121
Total	5,949,823	6,492,556
Derivative Liabilities, Fair Value	151,527	126,334
Securities sold not yet purchased	9,731	3,503
Total	161,258	129,837
Fair Value Measurement, Recurring [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Collateralized loan obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	346,466	345,952
Fair Value Measurement, Recurring [Member] \| U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	878	580
Available for sale securities	779,375	777,070
Fair Value Measurement, Recurring [Member] \| U.S. Treasury [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	878	580
Available for sale securities	779,375	777,070
Fair Value Measurement, Recurring [Member] \| U.S. Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	4,582	7,558
Available for sale securities	173,350	171,296
Fair Value Measurement, Recurring [Member] \| U.S. Agencies [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	4,582	7,558
Available for sale securities	173,350	171,296
Fair Value Measurement, Recurring [Member] \| Mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	480
Available for sale securities	3,479,951	3,982,122
Fair Value Measurement, Recurring [Member] \| Mortgage-backed [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	480
Available for sale securities	3,479,951	3,982,122
Fair Value Measurement, Recurring [Member] \| State and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	10,256	8,038
Available for sale securities	1,206,656	1,362,407
Fair Value Measurement, Recurring [Member] \| State and political subdivisions [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	10,256	8,038
Available for sale securities	1,206,656	1,362,407
Fair Value Measurement, Recurring [Member] \| Corporates [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	8,046	1,024
Available for sale securities	344,901	367,500
Fair Value Measurement, Recurring [Member] \| Corporates [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	8,046	1,024
Available for sale securities	$ 344,901	$ 367,500

Equity securities with readily determinable fair values.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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The carrying amount of a life insurance policy on an officer, executive or employee for which the reporting entity (a bank) is entitled to proceeds from the policy upon death of the insured or surrender of the insurance policy.

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- Definition

Fair value portion of arrangements with third parties, including, but not limited to, operating lease arrangement and arrangement in which the entity has agreed to expend funds to procure goods or services, or has agreed to commit resources to supply goods or services.

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Fair value, after offset of derivative liability, of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, before offset against an obligation to return collateral under a master netting arrangement. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Fair value, after offset of derivative asset, of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be and before offset against a right to receive collateral under a master netting arrangement. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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This item represents the amount that could be realized under a life insurance contract or contracts owned by the Entity as of the date of the statement of financial position. Such Entity-owned life insurance policies are commonly known as corporate-owned life insurance (COLI) or bank-owned life insurance (BOLI).

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- Definition

Fair value of financial instruments sold short by a broker-dealer for their own account (proprietary securities) for trading or investment purposes determined by management based upon quoted prices of a financial instrument with similar characteristics or on a valuation technique or model.

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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