Fair Value Measurements - Estimated Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and short-term investments	$ 5,352,599	$ 5,852,347
Available For Sale Securities Debt Securities	7,107,373	7,068,613
Securities held to maturity (exclusive of allowance for credit losses)	5,549,590	5,691,868
Trading securities	28,981	18,093
Other securities	447,650	492,935
Loans (exclusive of allowance for credit losses)	24,201,673	23,176,904
Derivatives	$ 211,971	$ 161,496
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]	Other Assets	Other Assets
Demand and savings deposits	$ 34,434,861	$ 32,719,268
Time deposits	2,082,709	3,073,591
Other borrowings	3,517,033	3,919,644
Long-term debt	384,245	383,247
Derivatives	$ 119,943	$ 105,083
Derivative Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities	Other Liabilities
Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and short-term investments	$ 5,352,599	$ 5,852,347
Available For Sale Securities Debt Securities	7,107,373	7,068,613
Securities held to maturity (exclusive of allowance for credit losses)	4,913,408	5,183,367
Trading securities	28,981	18,093
Other securities	447,650	492,935
Loans (exclusive of allowance for credit losses)	24,082,288	22,969,788
Derivatives	211,971	161,496
Demand and savings deposits	34,434,861	32,719,268
Time deposits	2,082,709	3,073,591
Other borrowings	3,517,033	3,919,644
Long-term debt	414,417	413,896
Derivatives	119,943	105,083
Commitments to extend credit for loans	5,666	11,523
Commitments to extend resell agreements	250	208
Commercial letters of credit	69	138
Standby letters of credit	2,097	4,047
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and short-term investments	5,105,137	5,612,003
Available For Sale Securities Debt Securities	1,123,425	1,650,017
Trading securities	9,152	2,873
Other securities	11,355	11,228
Demand and savings deposits	34,434,861	32,719,268
Other borrowings	25,740	13,813
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and short-term investments	247,462	240,344
Available For Sale Securities Debt Securities	5,983,948	5,418,596
Securities held to maturity (exclusive of allowance for credit losses)	4,913,408	5,183,367
Trading securities	19,829	15,220
Other securities	436,295	481,707
Loans (exclusive of allowance for credit losses)	24,082,288	22,969,788
Derivatives	211,971	161,496
Time deposits	2,082,709	3,073,591
Other borrowings	3,491,293	3,905,831
Long-term debt	414,417	413,896
Derivatives	$ 119,943	$ 105,083