v3.26.1
Securities - Gross Unrealized Losses and Fair Value of Investment Securities Available for Sale (Detail)
$ in Thousands
Jun. 30, 2026
USD ($)
Security
Dec. 31, 2025
USD ($)
Security
Gain (Loss) on Investments [Line Items]    
Less than 12 months, Count | Security 955 264
Less than 12 months, Fair Value $ 5,786,800 $ 1,519,913
Less than 12 months, Unrealized Losses $ (58,490) $ (17,173)
12 months or more, Count | Security 1,647 2,096
12 months or more, Fair Value $ 3,476,924 $ 3,878,183
12 months or more, Unrealized Losses $ (399,459) $ (391,573)
Total Count | Security 2,602 2,360
Total Fair Value $ 9,263,724 $ 5,398,096
Total Unrealized Losses $ (457,949) $ (408,746)
U.S. Treasury [Member]    
Gain (Loss) on Investments [Line Items]    
Less than 12 months, Count | Security 201 8
Less than 12 months, Fair Value $ 1,508,078 $ 72,013
Less than 12 months, Unrealized Losses $ (9,256) $ (88)
12 months or more, Count | Security 1 2
12 months or more, Fair Value $ 14,925 $ 30,234
12 months or more, Unrealized Losses $ (72) $ (353)
Total Count | Security 202 10
Total Fair Value $ 1,523,003 $ 102,247
Total Unrealized Losses $ (9,328) $ (441)
U.S. Agencies [Member]    
Gain (Loss) on Investments [Line Items]    
Less than 12 months, Count | Security 1 1
Less than 12 months, Fair Value $ 6,663 $ 7,855
Less than 12 months, Unrealized Losses $ (57) $ (100)
Total Count | Security 1 1
Total Fair Value $ 6,663 $ 7,855
Total Unrealized Losses $ (57) $ (100)
Mortgage-backed [Member]    
Gain (Loss) on Investments [Line Items]    
Less than 12 months, Count | Security 384 82
Less than 12 months, Fair Value $ 3,684,127 $ 757,160
Less than 12 months, Unrealized Losses $ (45,541) $ (5,682)
12 months or more, Count | Security 795 817
12 months or more, Fair Value $ 2,591,410 $ 2,871,729
12 months or more, Unrealized Losses $ (335,694) $ (325,469)
Total Count | Security 1,179 899
Total Fair Value $ 6,275,537 $ 3,628,889
Total Unrealized Losses $ (381,235) $ (331,151)
State and political subdivisions [Member]    
Gain (Loss) on Investments [Line Items]    
Less than 12 months, Count | Security 349 152
Less than 12 months, Fair Value $ 398,225 $ 515,364
Less than 12 months, Unrealized Losses $ (3,488) $ (11,181)
12 months or more, Count | Security 805 1,142
12 months or more, Fair Value $ 800,287 $ 809,113
12 months or more, Unrealized Losses $ (61,830) $ (61,666)
Total Count | Security 1,154 1,294
Total Fair Value $ 1,198,512 $ 1,324,477
Total Unrealized Losses $ (65,318) $ (72,847)
Corporates [Member]    
Gain (Loss) on Investments [Line Items]    
Less than 12 months, Count | Security   1
Less than 12 months, Fair Value   $ 2,990
Less than 12 months, Unrealized Losses   $ (10)
12 months or more, Count | Security 46 134
12 months or more, Fair Value $ 70,302 $ 164,108
12 months or more, Unrealized Losses $ (1,863) $ (4,078)
Total Count | Security 46 135
Total Fair Value $ 70,302 $ 167,098
Total Unrealized Losses $ (1,863) $ (4,088)
Collateralized loan obligations [Member]    
Gain (Loss) on Investments [Line Items]    
Less than 12 months, Count | Security 20 20
Less than 12 months, Fair Value $ 189,707 $ 164,531
Less than 12 months, Unrealized Losses $ (148) $ (112)
12 months or more, Count | Security   1
12 months or more, Fair Value   $ 2,999
12 months or more, Unrealized Losses   $ (7)
Total Count | Security 20 21
Total Fair Value $ 189,707 $ 167,530
Total Unrealized Losses $ (148) $ (119)