v3.26.3
Securities - Schedule of Fair Value and Amortized Cost of AFS and HTM Debt Securities (Detail) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost $ 3,669,420 $ 3,472,812
Available-for-sale, Gross Unrealized Gains 2,733 17,337
Available-for-sale, Gross Unrealized Losses (318,461) (201,817)
Available-for-sale, Fair Value 3,353,692 3,288,332
Held-to-maturity, Amortized Cost 1,094,139 1,132,114
Held-to-maturity, Gross Unrealized Gains 21 2,211
Held-to-maturity, Gross Unrealized Losses (169,957) (98,368)
Held-to-maturity securities, Fair value 924,203 1,035,957
Total debt securities, Amortized Cost 4,763,559 4,604,926
Total debt securities, Gross Unrealized Gains 2,754 19,548
Total debt securities, Gross Unrealized Losses (488,418) (300,185)
Total securities, Fair Value 4,277,895 4,324,289
U.S. Treasury [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost 197,154 196,586
Available-for-sale, Gross Unrealized Gains 0 271
Available-for-sale, Gross Unrealized Losses (444) 0
Available-for-sale, Fair Value 196,710 196,857
U.S. Government Sponsored Entities and Agencies [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost 225,388 243,408
Available-for-sale, Gross Unrealized Gains 0 212
Available-for-sale, Gross Unrealized Losses (27,660) (20,623)
Available-for-sale, Fair Value 197,728 222,997
Held-to-maturity, Amortized Cost 2,026 2,341
Held-to-maturity, Gross Unrealized Losses (176) (134)
Held-to-maturity securities, Fair value 1,850 2,207
Residential Mortgage-Backed Securities and Collateralized Mortgage Obligations of Government Sponsored Entities and Agencies [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost 3,006,963 2,771,608
Available-for-sale, Gross Unrealized Gains 2,180 15,149
Available-for-sale, Gross Unrealized Losses (279,896) (176,309)
Available-for-sale, Fair Value 2,729,247 2,610,448
Held-to-maturity, Amortized Cost 23,108 27,014
Held-to-maturity, Gross Unrealized Gains 1 2
Held-to-maturity, Gross Unrealized Losses (2,255) (1,547)
Held-to-maturity securities, Fair value 20,854 25,469
Commercial Mortgage-Backed Securities and Collateralized Mortgage Obligations of Government Sponsored Entities and Agencies [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost 56,268 66,043
Available-for-sale, Gross Unrealized Gains 0 233
Available-for-sale, Gross Unrealized Losses (3,618) (2,661)
Available-for-sale, Fair Value 52,650 63,615
Asset-Backed Securities [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost 63,743 69,095
Available-for-sale, Gross Unrealized Gains 41 45
Available-for-sale, Gross Unrealized Losses (183) (205)
Available-for-sale, Fair Value 63,601 68,935
Obligations of State and Political Subdivisions [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost 80,322 74,738
Available-for-sale, Gross Unrealized Gains 3 412
Available-for-sale, Gross Unrealized Losses (6,248) (1,962)
Available-for-sale, Fair Value 74,077 73,188
Held-to-maturity, Amortized Cost 1,067,030 1,100,788
Held-to-maturity, Gross Unrealized Gains 20 2,137
Held-to-maturity, Gross Unrealized Losses (167,517) (96,687)
Held-to-maturity securities, Fair value 899,533 1,006,238
Corporate Debt Securities [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost 39,582 51,334
Available-for-sale, Gross Unrealized Gains 509 1,015
Available-for-sale, Gross Unrealized Losses (412) (57)
Available-for-sale, Fair Value 39,679 52,292
Held-to-maturity, Amortized Cost 1,975 1,971
Held-to-maturity, Gross Unrealized Gains 0 72
Held-to-maturity, Gross Unrealized Losses (9)  
Held-to-maturity securities, Fair value $ 1,966 $ 2,043