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Investment Securities - Summary of Securities Available for Sale in an Unrealized Loss Position (Detail) - USD ($)
$ in Thousands
Dec. 31, 2025
Dec. 31, 2024
Schedule of Investments [Line Items]    
Less than 12 months, Fair Value $ 172,626 $ 219,109
Less than 12 months, Unrealized Losses 972 1,759
12 months or longer, Fair Value 1,998,999 2,238,628
12 months or longer, Unrealized Losses 215,667 322,178
Total, Fair Value 2,171,625 2,457,737
Total, Unrealized Losses 216,639 323,937
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 133 1,476
Less than 12 months, Unrealized Losses 1 3
12 months or longer, Fair Value 31,485 42,886
12 months or longer, Unrealized Losses 1,475 3,081
Total, Fair Value 31,618 44,362
Total, Unrealized Losses 1,476 3,084
State and Political Subdivisions [Member]    
Schedule of Investments [Line Items]    
Less than 12 months, Fair Value 6,177 3,314
Less than 12 months, Unrealized Losses 543 22
12 months or longer, Fair Value 483,564 479,681
12 months or longer, Unrealized Losses 55,091 79,493
Total, Fair Value 489,741 482,995
Total, Unrealized Losses 55,634 79,515
Residential Mortgage-Backed Securities, Agency [Member]    
Schedule of Investments [Line Items]    
Less than 12 months, Fair Value 109,848 128,655
Less than 12 months, Unrealized Losses 270 1,660
12 months or longer, Fair Value 795,183 856,448
12 months or longer, Unrealized Losses 114,047 165,454
Total, Fair Value 905,031 985,103
Total, Unrealized Losses 114,317 167,114
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 21,189 59,668
12 months or longer, Unrealized Losses 4,237 6,531
Total, Fair Value 21,189 59,668
Total, Unrealized Losses 4,237 6,531
Commercial Mortgage-Backed Securities Agency [Member]    
Schedule of Investments [Line Items]    
Less than 12 months, Fair Value 6,287 0
Less than 12 months, Unrealized Losses 4 0
12 months or longer, Fair Value 293,038 319,506
12 months or longer, Unrealized Losses 26,048 42,698
Total, Fair Value 299,325 319,506
Total, Unrealized Losses 26,052 42,698
Asset-backed Securities [Member]    
Schedule of Investments [Line Items]    
Less than 12 months, Fair Value 50,181 83,188
Less than 12 months, Unrealized Losses 154 50
12 months or longer, Fair Value 136,940 215,886
12 months or longer, Unrealized Losses 2,227 1,997
Total, Fair Value 187,121 299,074
Total, Unrealized Losses 2,381 2,047
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 12,658 11,919
12 months or longer, Unrealized Losses 661 1,377
Total, Fair Value 12,658 11,919
Total, Unrealized Losses 661 1,377
Other Corporate Securities [Member]    
Schedule of Investments [Line Items]    
Less than 12 months, Fair Value 0 2,476
Less than 12 months, Unrealized Losses 0 24
12 months or longer, Fair Value 224,942 252,634
12 months or longer, Unrealized Losses 11,881 21,547
Total, Fair Value 224,942 255,110
Total, Unrealized Losses $ 11,881 $ 21,571