v3.26.1
Investment Securities - Summary of Securities Available for Sale in an Unrealized Loss Position (Detail) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Schedule of Investments [Line Items]    
Less than 12 months, Fair Value $ 781,330 $ 172,626
Less than 12 months, Unrealized Losses 11,399 972
12 months or longer, Fair Value 1,808,348 1,998,999
12 months or longer, Unrealized Losses 207,090 215,667
Total, Fair Value 2,589,678 2,171,625
Total, Unrealized Losses 218,489 216,639
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member]    
Schedule of Investments [Line Items]    
Less than 12 months, Fair Value 396 133
Less than 12 months, Unrealized Losses 1 1
12 months or longer, Fair Value 30,034 31,485
12 months or longer, Unrealized Losses 1,397 1,475
Total, Fair Value 30,430 31,618
Total, Unrealized Losses 1,398 1,476
State and Political Subdivisions [Member]    
Schedule of Investments [Line Items]    
Less than 12 months, Fair Value 10,055 6,177
Less than 12 months, Unrealized Losses 930 543
12 months or longer, Fair Value 474,897 483,564
12 months or longer, Unrealized Losses 54,952 55,091
Total, Fair Value 484,952 489,741
Total, Unrealized Losses 55,882 55,634
Residential Mortgage-Backed Securities, Agency [Member]    
Schedule of Investments [Line Items]    
Less than 12 months, Fair Value 732,079 109,848
Less than 12 months, Unrealized Losses 10,361 270
12 months or longer, Fair Value 728,665 795,183
12 months or longer, Unrealized Losses 117,007 114,047
Total, Fair Value 1,460,744 905,031
Total, Unrealized Losses 127,368 114,317
Residential Mortgage-Backed Securities, Non-agency [Member]    
Schedule of Investments [Line Items]    
Less than 12 months, Fair Value 0 0
Less than 12 months, Unrealized Losses 0 0
12 months or longer, Fair Value 21,302 21,189
12 months or longer, Unrealized Losses 4,060 4,237
Total, Fair Value 21,302 21,189
Total, Unrealized Losses 4,060 4,237
Commercial Mortgage-Backed Securities Agency [Member]    
Schedule of Investments [Line Items]    
Less than 12 months, Fair Value 4,327 6,287
Less than 12 months, Unrealized Losses 38 4
12 months or longer, Fair Value 217,727 293,038
12 months or longer, Unrealized Losses 17,684 26,048
Total, Fair Value 222,054 299,325
Total, Unrealized Losses 17,722 26,052
Asset-backed Securities [Member]    
Schedule of Investments [Line Items]    
Less than 12 months, Fair Value 28,506 50,181
Less than 12 months, Unrealized Losses 40 154
12 months or longer, Fair Value 130,309 136,940
12 months or longer, Unrealized Losses 2,081 2,227
Total, Fair Value 158,815 187,121
Total, Unrealized Losses 2,121 2,381
Single Issue Trust Preferred Securities [Member]    
Schedule of Investments [Line Items]    
Less than 12 months, Fair Value 0 0
Less than 12 months, Unrealized Losses 0 0
12 months or longer, Fair Value 12,958 12,658
12 months or longer, Unrealized Losses 372 661
Total, Fair Value 12,958 12,658
Total, Unrealized Losses 372 661
Other Corporate Securities [Member]    
Schedule of Investments [Line Items]    
Less than 12 months, Fair Value 5,967 0
Less than 12 months, Unrealized Losses 29 0
12 months or longer, Fair Value 192,456 224,942
12 months or longer, Unrealized Losses 9,537 11,881
Total, Fair Value 198,423 224,942
Total, Unrealized Losses $ 9,566 $ 11,881