v3.26.3
Securities - Schedule of Unrealized Losses on Investment Securities (Detail)
$ in Thousands
Sep. 30, 2026
USD ($)
Security
Dec. 31, 2025
USD ($)
Security
Net Unrealized Gains And Losses On Investments [Line Items]    
Less than 12 months, Fair Value $ 1,824,084 $ 327,278
Less than 12 months, Unrealized Losses $ (70,287) $ (1,833)
Less than 12 months, Number of Securities | Security 449 89
12 months or more, Fair Value $ 1,389,780 $ 1,574,675
12 months or more, Unrealized Losses $ (248,174) $ (199,984)
12 months or more, Number of Securities | Security 438 525
Fair Value, Total $ 3,213,864 $ 1,901,953
Unrealized Losses, Total $ (318,461) $ (201,817)
Number of Securities Total | Security 887 614
U.S. Treasury [Member]    
Net Unrealized Gains And Losses On Investments [Line Items]    
Less than 12 months, Fair Value $ 196,711 $ 0
Less than 12 months, Unrealized Losses $ (444) $ 0
Less than 12 months, Number of Securities | Security 4 0
12 months or more, Fair Value $ 0 $ 0
12 months or more, Unrealized Losses $ 0 $ 0
12 months or more, Number of Securities | Security 0 0
Fair Value, Total $ 196,711 $ 0
Unrealized Losses, Total $ (444) $ 0
Number of Securities Total | Security 4 0
U.S. Government Sponsored Entities and Agencies [Member]    
Net Unrealized Gains And Losses On Investments [Line Items]    
Less than 12 months, Fair Value $ 29,183 $ 8,252
Less than 12 months, Unrealized Losses $ (1,590) $ (109)
Less than 12 months, Number of Securities | Security 6 3
12 months or more, Fair Value $ 168,546 $ 189,841
12 months or more, Unrealized Losses $ (26,070) $ (20,514)
12 months or more, Number of Securities | Security 38 42
Fair Value, Total $ 197,729 $ 198,093
Unrealized Losses, Total $ (27,660) $ (20,623)
Number of Securities Total | Security 44 45
Residential Mortgage-Backed Securities and Collateralized Mortgage Obligations of Government Sponsored Entities and Agencies [Member]    
Net Unrealized Gains And Losses On Investments [Line Items]    
Less than 12 months, Fair Value $ 1,473,938 $ 245,766
Less than 12 months, Unrealized Losses $ (64,171) $ (1,340)
Less than 12 months, Number of Securities | Security 332 59
12 months or more, Fair Value $ 1,148,750 $ 1,307,219
12 months or more, Unrealized Losses $ (215,725) $ (174,969)
12 months or more, Number of Securities | Security 355 430
Fair Value, Total $ 2,622,688 $ 1,552,985
Unrealized Losses, Total $ (279,896) $ (176,309)
Number of Securities Total | Security 687 489
Commercial Mortgage-Backed Securities and Collateralized Mortgage Obligations of Government Sponsored Entities and Agencies [Member]    
Net Unrealized Gains And Losses On Investments [Line Items]    
Less than 12 months, Fair Value $ 14,508 $ 0
Less than 12 months, Unrealized Losses $ (564) $ 0
Less than 12 months, Number of Securities | Security 4 0
12 months or more, Fair Value $ 38,142 $ 48,325
12 months or more, Unrealized Losses $ (3,054) $ (2,661)
12 months or more, Number of Securities | Security 16 18
Fair Value, Total $ 52,650 $ 48,325
Unrealized Losses, Total $ (3,618) $ (2,661)
Number of Securities Total | Security 20 18
Asset-Backed Securities [Member]    
Net Unrealized Gains And Losses On Investments [Line Items]    
Less than 12 months, Fair Value $ 40,916 $ 58,042
Less than 12 months, Unrealized Losses $ (151) $ (205)
Less than 12 months, Number of Securities | Security 8 11
12 months or more, Fair Value $ 7,689 $ 0
12 months or more, Unrealized Losses $ (32) $ 0
12 months or more, Number of Securities | Security 2 0
Fair Value, Total $ 48,605 $ 58,042
Unrealized Losses, Total $ (183) $ (205)
Number of Securities Total | Security 10 11
Obligations of State and Political Subdivisions [Member]    
Net Unrealized Gains And Losses On Investments [Line Items]    
Less than 12 months, Fair Value $ 49,921 $ 4,168
Less than 12 months, Unrealized Losses $ (2,981) $ (124)
Less than 12 months, Number of Securities | Security 84 8
12 months or more, Fair Value $ 19,183 $ 23,806
12 months or more, Unrealized Losses $ (3,267) $ (1,838)
12 months or more, Number of Securities | Security 25 33
Fair Value, Total $ 69,104 $ 27,974
Unrealized Losses, Total $ (6,248) $ (1,962)
Number of Securities Total | Security 109 41
Corporate Debt Securities [Member]    
Net Unrealized Gains And Losses On Investments [Line Items]    
Less than 12 months, Fair Value $ 18,907 $ 11,050
Less than 12 months, Unrealized Losses $ (386) $ (55)
Less than 12 months, Number of Securities | Security 11 8
12 months or more, Fair Value $ 7,470 $ 5,484
12 months or more, Unrealized Losses $ (26) $ (2)
12 months or more, Number of Securities | Security 2 2
Fair Value, Total $ 26,377 $ 16,534
Unrealized Losses, Total $ (412) $ (57)
Number of Securities Total | Security 13 10