Fair Value Measurements - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024	Jun. 30, 2024	Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 7,116,087	$ 10,234,258	$ 7,144,784	$ 8,687,276
Securities held to maturity, net of allowance for credit losses of $310 at both June 30, 2025 and December 31, 2024	3,486,290	3,533,775
Deposits	41,683,614	42,722,748
Federal funds purchased	25,700	21,975
Repurchase agreements	4,418,379	4,342,941
Junior subordinated deferrable interest debentures	123,213	123,184
Subordinated notes	99,726	99,648
Loans, net	20,976,692	20,484,662
Carrying Amount [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	7,116,087	10,234,258
Securities held to maturity, net of allowance for credit losses of $310 at both June 30, 2025 and December 31, 2024	3,486,290	3,533,775
Accrued interest receivable	247,257	236,591
Deposits	41,683,614	42,722,748
Federal funds purchased	25,700	21,975
Repurchase agreements	4,418,379	4,342,941
Junior subordinated deferrable interest debentures	123,213	123,184
Subordinated notes	99,726	99,648
Accrued interest payable	52,938	58,870
Carrying Amount [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	20,976,692	20,484,662
Estimated Fair Value [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	7,116,087	10,234,258
Securities held to maturity, net of allowance for credit losses of $310 at both June 30, 2025 and December 31, 2024	3,218,209	3,360,546
Accrued interest receivable	247,257	236,591
Deposits	41,672,001	42,712,907
Federal funds purchased	25,700	21,975
Repurchase agreements	4,418,379	4,342,941
Junior subordinated deferrable interest debentures	123,712	123,712
Subordinated notes	97,679	98,453
Accrued interest payable	52,938	58,870
Estimated Fair Value [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	$ 20,688,014	$ 20,066,512

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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Amount, after allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

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Amount of short term borrowing where a bank borrows, at the federal funds rate, from another bank.

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Amortized cost excluding accrued interest, after allowance for credit loss, of financing receivable. Excludes net investment in lease.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of long-term debt (with maturities initially due after one year or beyond the operating cycle if longer) identified as Junior Subordinated Notes, which have a lower priority than senior instruments.

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