Fair Value Measurements - Summary of Estimated Fair Values of Significant Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Held-to-maturity investment securities, Fair Value	$ 7,291,244	$ 7,453,123
Carrying Amount | Fair Value, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	2,993,919	2,074,434
Held-to-maturity investment securities, Carrying Amount	8,192,720	8,444,191
Loans and leases, net	52,949,913	51,815,602
Securities sold under agreements to repurchase and federal funds purchased	372,806	344,168
FHLB advances	3,339,914	2,110,108
Long-term debt	905,634	909,185
Carrying Amount | Fair Value, Nonrecurring | Deposit liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits	58,394,540	56,518,126
Carrying Amount | Fair Value, Nonrecurring | Time deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits	7,919,885	8,234,954
Level 1 | Fair Value | Fair Value, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	2,993,919	2,074,434
Level 2 | Fair Value | Fair Value, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Held-to-maturity investment securities, Fair Value	7,291,244	7,453,123
Securities sold under agreements to repurchase and federal funds purchased	372,858	344,166
FHLB advances	3,337,057	2,107,790
Long-term debt	909,945	860,200
Level 2 | Fair Value | Fair Value, Nonrecurring | Deposit liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits	58,394,540	56,518,126
Level 2 | Fair Value | Fair Value, Nonrecurring | Time deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deposits	7,895,161	8,211,582
Level 3 | Fair Value | Fair Value, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans and leases, net	$ 51,416,732	$ 50,245,305