Fair Value Measurements (Estimated Fair Values of Financial Instruments) (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and cash equivalents	$ 10,234,258	$ 8,687,276	$ 12,028,132	$ 16,583,000
Securities held to maturity	3,533,775	3,619,428
Deposits	42,722,748	41,920,568
Federal funds purchased	21,975	14,200
Repurchase agreements	4,342,941	4,127,188
Junior subordinated deferrable interest debentures	123,184	123,127
Subordinated notes	99,648	99,491
Net loans	20,484,662	18,578,255
Carrying Amount [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and cash equivalents	10,234,258	8,687,276
Securities held to maturity	3,533,775	3,619,428
Accrued interest receivable	236,591	251,385
Deposits	42,722,748	41,920,568
Federal funds purchased	21,975	14,200
Repurchase agreements	4,342,941	4,127,188
Junior subordinated deferrable interest debentures	123,184	123,127
Subordinated notes	99,648	99,491
Accrued interest payable	58,870	61,222
Carrying Amount [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net loans	20,484,662	18,578,255
Estimated Fair Value [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and cash equivalents	10,234,258	8,687,276
Securities held to maturity	3,360,546	3,532,044
Accrued interest receivable	236,591	251,385
Deposits	42,712,907	41,903,580
Federal funds purchased	21,975	14,200
Repurchase agreements	4,342,941	4,127,188
Junior subordinated deferrable interest debentures	123,712	123,712
Subordinated notes	98,453	96,071
Accrued interest payable	58,870	61,222
Estimated Fair Value [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net loans	$ 20,066,512	$ 18,117,369

Amount of cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage. Excludes amount for disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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