v3.26.3
Fair Value Measurements - Summary of Estimated Fair Values of Financial Instruments (Detail) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and cash equivalents $ 1,882,389 $ 2,542,250
Securities available for sale 3,500,495 3,059,452
Securities held to maturity 1,007 1,004
Other securities 314,674 305,184
Loans held for sale 17,712 31,277
Net loans 25,460,258 24,709,122
Derivative financial assets 1,174 789
Deposits 27,710,734 27,060,939
Derivative financial liabilities 0 70
Carrying Amount [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and cash equivalents 1,882,389 2,542,250
Securities available for sale 3,500,495 3,059,452
Securities held to maturity 1,007 1,004
Other securities 314,674 305,184
Loans held for sale 17,712 31,277
Net loans 25,166,112 24,411,604
Derivative financial assets 1,174 789
Deposits 27,710,734 27,060,939
Short-term borrowings 184,810 198,573
Long-term borrowings 533,011 531,817
Derivative financial liabilities 0 70
Carrying Amount [Member] | Marketable Equity Securities [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Equity securities 25,765 34,760
Fair Value [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and cash equivalents 1,882,389 2,542,250
Securities available for sale 3,500,495 3,059,452
Securities held to maturity 1,020 1,020
Other securities 298,940 289,925
Loans held for sale 17,712 31,277
Net loans 24,768,971 24,432,980
Derivative financial assets 1,174 789
Deposits 27,662,016 27,031,873
Short-term borrowings 184,810 198,573
Long-term borrowings 528,764 524,281
Derivative financial liabilities 0 70
Fair Value [Member] | Marketable Equity Securities [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Equity securities 25,765 34,760
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and cash equivalents 0 0
Securities available for sale 4,431 4,678
Securities held to maturity 0 0
Other securities 0 0
Loans held for sale 0 0
Net loans 0 0
Derivative financial assets 0 0
Deposits 0 0
Short-term borrowings 0 0
Long-term borrowings 0 0
Derivative financial liabilities 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Marketable Equity Securities [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Equity securities 25,765 29,356
Significant Other Observable Inputs (Level 2) [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and cash equivalents 1,882,389 2,542,250
Securities available for sale 3,496,064 3,054,774
Securities held to maturity 0 0
Other securities 0 0
Loans held for sale 0 0
Net loans 0 0
Derivative financial assets 543 316
Deposits 27,662,016 27,031,873
Short-term borrowings 184,810 198,573
Long-term borrowings 528,764 524,281
Derivative financial liabilities 0 70
Significant Other Observable Inputs (Level 2) [Member] | Marketable Equity Securities [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Equity securities 0 5,404
Significant Unobservable Inputs (Level 3) [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and cash equivalents 0 0
Securities available for sale 0 0
Securities held to maturity 1,020 1,020
Other securities 298,940 289,925
Loans held for sale 17,712 31,277
Net loans 24,768,971 24,432,980
Derivative financial assets 631 473
Deposits 0 0
Short-term borrowings 0 0
Long-term borrowings 0 0
Derivative financial liabilities 0 0
Significant Unobservable Inputs (Level 3) [Member] | Marketable Equity Securities [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Equity securities $ 0 $ 0