v3.26.1
Securities - Schedule of Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Securities by Contractual Maturity (Detail) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Amortized Cost and Fair Value Debt Securities [Line Items]    
Total available-for-sale debt securities at amortized cost, Within one year $ 213,587  
Total available-for-sale debt securities at amortized cost, After 1 year through 5 years 209,743  
Total available-for-sale debt securities at amortized cost, After 5 years through 10 years 350,280  
Total available-for-sale debt securities, Amortized Cost, After 10 years 2,748,400  
Available-for-sale, Amortized Cost 3,522,010 $ 3,472,812
Total held-to-maturity debt securities at amortized cost, Within one year 13,390  
Total held-to-maturity debt securities at amortized cost, After 1 year through 5 years 264,076  
Total held-to-maturity debt securities at amortized cost, After 5 years through 10 years 570,529  
Total held-to-maturity debt securities at amortized cost, After 10 years 259,756  
Held-to-maturity, Amortized Cost 1,107,751 1,132,114
Total debt securities, Amortized Cost 4,629,761 4,604,926
Total available-for-sale debt securities, Fair value, Within one year 213,302  
Total available-for-sale debt securities, Fair value, After 1 year through 5 years 202,122  
Total available-for-sale debt securities, Fair value, After 5 years through 10 years 324,289  
Total available-for-sale debt securities, Fair value, After 10 years 2,573,259  
Total available-for-sale debt securities, Fair value 3,312,972 3,288,332
Total held-to-maturity debt securities, Fair value, Within one year 13,375  
Total held-to-maturity debt securities, Fair value, After 1 year through 5 years 257,544  
Total held-to-maturity debt securities, Fair value, After 5 years through 10 years 512,025  
Total held-to-maturity debt securities, Fair value, After 10 years 222,781  
Total held-to-maturity debt securities, Fair value 1,005,725 1,035,957
Total debt securities, Fair Value $ 4,318,697 4,324,289
Available-for-sale debt securities, Weighted-average yield, Within One Year 3.67%  
Available-for-sale debt securities, Weighted-average yield, After 1 Year through 5 Years 3.38%  
Available-for-sale debt securities, Weighted-average yield, After 5 Years through 10 Years 2.53%  
Available-for-sale debt securities, Weighted-average yield, After 10 Years 3.48%  
Available-for-sale debt securities, Total 3.39%  
Held-to-maturity debt securities, Weighted-average yield, Within One Year 4.05%  
Held-to-maturity debt securities, Weighted-average yield, After 1 Year through 5 Years 3.54%  
Held-to-maturity debt securities, Weighted-average yield, After 5 Years through 10 Years 2.84%  
Held-to-maturity debt securities, Weighted-average yield, After 10 Years 2.96%  
Held-to-maturity debt securities, Weighted-average yield, Total 3.05%  
U.S. Treasury [Member]    
Amortized Cost and Fair Value Debt Securities [Line Items]    
Total available-for-sale debt securities at amortized cost, Within one year $ 196,162  
Available-for-sale, Amortized Cost 196,162 196,586
Total available-for-sale debt securities, Fair value 195,957 196,857
U.S. Government Sponsored Entities and Agencies [Member]    
Amortized Cost and Fair Value Debt Securities [Line Items]    
Total available-for-sale debt securities at amortized cost, Within one year 4,164  
Total available-for-sale debt securities at amortized cost, After 1 year through 5 years 87,936  
Total available-for-sale debt securities at amortized cost, After 5 years through 10 years 33,029  
Total available-for-sale debt securities, Amortized Cost, After 10 years 106,526  
Available-for-sale, Amortized Cost 231,655 243,408
Total held-to-maturity debt securities at amortized cost, After 1 year through 5 years 606  
Total held-to-maturity debt securities at amortized cost, After 5 years through 10 years 1,311  
Total held-to-maturity debt securities at amortized cost, After 10 years 156  
Held-to-maturity, Amortized Cost 2,073 2,341
Total available-for-sale debt securities, Fair value 211,065 222,997
Total held-to-maturity debt securities, Fair value 1,931 2,207
Residential Mortgage-Backed Securities and Collateralized Mortgage Obligations of Government Sponsored Entities and Agencies [Member]    
Amortized Cost and Fair Value Debt Securities [Line Items]    
Total available-for-sale debt securities at amortized cost, Within one year 70  
Total available-for-sale debt securities at amortized cost, After 1 year through 5 years 25,582  
Total available-for-sale debt securities at amortized cost, After 5 years through 10 years 291,873  
Total available-for-sale debt securities, Amortized Cost, After 10 years 2,534,098  
Available-for-sale, Amortized Cost 2,851,623 2,771,608
Total held-to-maturity debt securities at amortized cost, After 1 year through 5 years 2,072  
Total held-to-maturity debt securities at amortized cost, After 5 years through 10 years 5,030  
Total held-to-maturity debt securities at amortized cost, After 10 years 17,343  
Held-to-maturity, Amortized Cost 24,445 27,014
Total available-for-sale debt securities, Fair value 2,667,319 2,610,448
Total held-to-maturity debt securities, Fair value 22,737 25,469
Commercial Mortgage-Backed Securities and Collateralized Mortgage Obligations of Government Sponsored Entities and Agencies [Member]    
Amortized Cost and Fair Value Debt Securities [Line Items]    
Total available-for-sale debt securities at amortized cost, Within one year 2,042  
Total available-for-sale debt securities at amortized cost, After 1 year through 5 years 30,296  
Total available-for-sale debt securities at amortized cost, After 5 years through 10 years 3,955  
Total available-for-sale debt securities, Amortized Cost, After 10 years 20,905  
Available-for-sale, Amortized Cost 57,198 66,043
Total available-for-sale debt securities, Fair value 54,600 63,615
Asset Backed Securities [Member]    
Amortized Cost and Fair Value Debt Securities [Line Items]    
Total available-for-sale debt securities, Amortized Cost, After 10 years 65,186  
Available-for-sale, Amortized Cost 65,186 69,095
Total available-for-sale debt securities, Fair value 64,994 68,935
Obligations of State and Political Subdivisions [Member]    
Amortized Cost and Fair Value Debt Securities [Line Items]    
Total available-for-sale debt securities at amortized cost, Within one year 2,157  
Total available-for-sale debt securities at amortized cost, After 1 year through 5 years 37,722  
Total available-for-sale debt securities at amortized cost, After 5 years through 10 years 17,676  
Total available-for-sale debt securities, Amortized Cost, After 10 years 21,685  
Available-for-sale, Amortized Cost 79,240 74,738
Total held-to-maturity debt securities at amortized cost, Within one year 13,390  
Total held-to-maturity debt securities at amortized cost, After 1 year through 5 years 259,424  
Total held-to-maturity debt securities at amortized cost, After 5 years through 10 years 564,188  
Total held-to-maturity debt securities at amortized cost, After 10 years 242,257  
Held-to-maturity, Amortized Cost 1,079,259 1,100,788
Total available-for-sale debt securities, Fair value 77,432 73,188
Total held-to-maturity debt securities, Fair value 979,040 1,006,238
Corporate Debt Securities [Member]    
Amortized Cost and Fair Value Debt Securities [Line Items]    
Total available-for-sale debt securities at amortized cost, Within one year 8,992  
Total available-for-sale debt securities at amortized cost, After 1 year through 5 years 28,207  
Total available-for-sale debt securities at amortized cost, After 5 years through 10 years 3,747  
Available-for-sale, Amortized Cost 40,946 51,334
Total held-to-maturity debt securities at amortized cost, After 1 year through 5 years 1,974  
Held-to-maturity, Amortized Cost 1,974 1,971
Total available-for-sale debt securities, Fair value 41,605 52,292
Total held-to-maturity debt securities, Fair value $ 2,017 $ 2,043