v3.26.1
Securities - Schedule of Fair Value and Amortized Cost of Available-for-sale and Held-to-maturity Securities (Detail) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost $ 3,522,010 $ 3,472,812
Available-for-sale, Gross Unrealized Gains 8,417 17,337
Available-for-sale, Gross Unrealized Losses (217,455) (201,817)
Available-for-sale, Fair Value 3,312,972 3,288,332
Held-to-maturity, Amortized Cost 1,107,751 1,132,114
Held-to-maturity, Gross Unrealized Gains 1,980 2,211
Held-to-maturity, Gross Unrealized Losses (104,006) (98,368)
Held-to-maturity securities, Fair value 1,005,725 1,035,957
Total debt securities, Amortized Cost 4,629,761 4,604,926
Total debt securities, Gross Unrealized Gains 10,397 19,548
Total debt securities, Gross Unrealized Losses (321,461) (300,185)
Total securities, Fair Value 4,318,697 4,324,289
U.S. Treasury [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost 196,162 196,586
Available-for-sale, Gross Unrealized Gains 0 271
Available-for-sale, Gross Unrealized Losses (205) 0
Available-for-sale, Fair Value 195,957 196,857
U.S. Government Sponsored Entities and Agencies [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost 231,655 243,408
Available-for-sale, Gross Unrealized Gains 200 212
Available-for-sale, Gross Unrealized Losses (20,790) (20,623)
Available-for-sale, Fair Value 211,065 222,997
Held-to-maturity, Amortized Cost 2,073 2,341
Held-to-maturity, Gross Unrealized Losses (142) (134)
Held-to-maturity securities, Fair value 1,931 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 2,851,623 2,771,608
Available-for-sale, Gross Unrealized Gains 7,134 15,149
Available-for-sale, Gross Unrealized Losses (191,438) (176,309)
Available-for-sale, Fair Value 2,667,319 2,610,448
Held-to-maturity, Amortized Cost 24,445 27,014
Held-to-maturity, Gross Unrealized Gains 1 2
Held-to-maturity, Gross Unrealized Losses (1,709) (1,547)
Held-to-maturity securities, Fair value 22,737 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 57,198 66,043
Available-for-sale, Gross Unrealized Gains 14 233
Available-for-sale, Gross Unrealized Losses (2,612) (2,661)
Available-for-sale, Fair Value 54,600 63,615
Asset-Backed Securities [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost 65,186 69,095
Available-for-sale, Gross Unrealized Gains 27 45
Available-for-sale, Gross Unrealized Losses (219) (205)
Available-for-sale, Fair Value 64,994 68,935
Obligations of State and Political Subdivisions [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost 79,240 74,738
Available-for-sale, Gross Unrealized Gains 307 412
Available-for-sale, Gross Unrealized Losses (2,115) (1,962)
Available-for-sale, Fair Value 77,432 73,188
Held-to-maturity, Amortized Cost 1,079,259 1,100,788
Held-to-maturity, Gross Unrealized Gains 1,936 2,137
Held-to-maturity, Gross Unrealized Losses (102,155) (96,687)
Held-to-maturity securities, Fair value 979,040 1,006,238
Corporate Debt Securities [Member]    
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Available-for-sale, Amortized Cost 40,946 51,334
Available-for-sale, Gross Unrealized Gains 735 1,015
Available-for-sale, Gross Unrealized Losses (76) (57)
Available-for-sale, Fair Value 41,605 52,292
Held-to-maturity, Amortized Cost 1,974 1,971
Held-to-maturity, Gross Unrealized Gains 43 72
Held-to-maturity securities, Fair value $ 2,017 $ 2,043