Fair Value Measurements - Estimated Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and short-term investments	$ 7,210,342	$ 5,852,347
Available For Sale Securities Debt Securities	6,541,391	7,068,613
Held To Maturity Securities	5,626,437	5,691,868
Trading securities	40,187	18,093
Other securities	473,434	492,935
Loans (exclusive of allowance for credit losses)	$ 23,642,064	$ 23,176,904
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Derivatives	$ 220,913	$ 161,496
Demand and savings deposits	34,270,001	32,719,268
Time deposits	2,643,609	3,073,591
Other borrowings	4,025,474	3,919,644
Long-term debt	$ 383,742	$ 383,247
Derivative Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other liabilities	Other liabilities
Derivatives	$ 119,529	$ 105,083
Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and short-term investments	7,210,342	5,852,347
Available For Sale Securities Debt Securities	6,541,391	7,068,613
Held To Maturity Securities	5,025,138	5,183,367
Trading securities	40,187	18,093
Other securities	473,434	492,935
Loans (exclusive of allowance for credit losses)	23,505,767	22,969,788
Derivatives	220,913	161,496
Demand and savings deposits	34,270,001	32,719,268
Time deposits	2,643,609	3,073,591
Other borrowings	4,025,474	3,919,644
Long-term debt	414,919	413,896
Derivatives	119,529	105,083
Commitments to extend credit for loans	2,908	11,523
Commitments to extend resell agreements	125	208
Commercial letters of credit	32	138
Standby letters of credit	1,024	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	7,030,067	5,612,003
Available For Sale Securities Debt Securities	1,132,537	1,650,017
Trading securities	8,520	2,873
Other securities	11,292	11,228
Demand and savings deposits	34,270,001	32,719,268
Other borrowings	47,908	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	180,275	240,344
Available For Sale Securities Debt Securities	5,408,854	5,418,596
Held To Maturity Securities	5,025,138	5,183,367
Trading securities	31,667	15,220
Other securities	462,142	481,707
Loans (exclusive of allowance for credit losses)	23,505,767	22,969,788
Derivatives	220,913	161,496
Time deposits	2,643,609	3,073,591
Other borrowings	3,977,566	3,905,831
Long-term debt	414,919	413,896
Derivatives	$ 119,529	$ 105,083