v3.26.1
Fair Value Measurements - Estimated Fair Value of Financial Instruments (Detail) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash and short-term investments $ 6,659,324 $ 9,441,175
Securities available for sale 13,488,159 13,709,141
Securities held to maturity (exclusive of allowance for credit losses) 5,716,426 5,724,227
Trading securities 45,839 22,331
Other securities 693,502 676,300
Loans (exclusive of allowance for credit losses) 41,156,526 38,781,438
Derivatives $ 236,420 $ 281,329
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration] Other Assets Other Assets
Time deposits $ 3,207,902 $ 3,760,862
Other borrowings 3,083,600 3,324,938
Long-term debt 480,126 474,229
Derivatives $ 148,337 $ 136,452
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 $ 6,659,324 $ 9,441,175
Securities available for sale 13,488,159 13,709,141
Securities held to maturity (exclusive of allowance for credit losses) 5,239,447 5,250,465
Trading securities 45,839 22,331
Other securities 693,502 676,300
Loans (exclusive of allowance for credit losses) 40,602,007 39,041,201
Derivatives 236,420 281,329
Time deposits 3,223,265 3,760,862
Other borrowings 3,083,600 3,324,938
Long-term debt 489,896 523,545
Derivatives 148,337 136,452
Commitments to extend credit for loans 9,411 14,972
Commitments to extend resell agreements 435 106
Commercial letters of credit 32 130
Standby letters of credit 2,851 4,483
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 5,730,886 7,893,082
Securities available for sale 2,292,226 2,497,930
Trading securities 11,355 5,145
Other securities 12,610 14,690
Other borrowings 24,520 32,133
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 928,438 1,548,093
Securities available for sale 11,195,933 11,211,211
Securities held to maturity (exclusive of allowance for credit losses) 5,239,447 5,250,465
Trading securities 34,484 17,186
Other securities 680,892 661,610
Loans (exclusive of allowance for credit losses) 40,602,007 39,041,201
Derivatives 236,420 281,329
Time deposits 3,223,265 3,760,862
Other borrowings 3,059,080 3,292,805
Long-term debt 489,896 523,545
Derivatives $ 148,337 $ 136,452