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Investment Securities - Gross Unrealized Losses on Debt Securities (Detail) - USD ($) $ in Thousands | Jun. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Debt Securities Available for Sale |  |
Less than 12 months, fair value | $ 89,924 | $ 117,107
Less than 12 months, unrealized loss | (795) | (1,029)
12 months or more, fair value | 1,483,181 | 1,546,730
12 months or more, unrealized loss | (189,803) | (233,626)
Total, fair value | 1,573,105 | 1,663,837
Total, unrealized loss | (190,598) | (234,655)
Debt Securities Held to Maturity |  |
Less than 12 months, fair value | 0 | 0
Less than 12 months, unrealized loss | 0 | 0
12 months or more, fair value | 95,644 | 103,038
12 months or more, unrealized loss | (4,703) | (7,522)
Total, fair value | 95,644 | 103,038
Total, unrealized loss | (4,703) | (7,522)
Obligations of U.S. government agencies |  |
Debt Securities Available for Sale |  |
Less than 12 months, fair value | 12,636 | 63,714
Less than 12 months, unrealized loss | (54) | (842)
12 months or more, fair value | 992,579 | 1,021,654
12 months or more, unrealized loss | (135,863) | (173,643)
Total, fair value | 1,005,215 | 1,085,368
Total, unrealized loss | (135,917) | (174,485)
Debt Securities Held to Maturity |  |
Less than 12 months, fair value | 0 | 0
Less than 12 months, unrealized loss | 0 | 0
12 months or more, fair value | 94,137 | 101,553
12 months or more, unrealized loss | (4,646) | (7,443)
Total, fair value | 94,137 | 101,553
Total, unrealized loss | (4,646) | (7,443)
Obligations of states and political subdivisions |  |
Debt Securities Available for Sale |  |
Less than 12 months, fair value | 10,508 | 7,457
Less than 12 months, unrealized loss | (401) | (140)
12 months or more, fair value | 198,470 | 208,063
12 months or more, unrealized loss | (27,781) | (28,809)
Total, fair value | 208,978 | 215,520
Total, unrealized loss | (28,182) | (28,949)
Debt Securities Held to Maturity |  |
Less than 12 months, fair value | 0 | 0
Less than 12 months, unrealized loss | 0 | 0
12 months or more, fair value | 1,507 | 1,485
12 months or more, unrealized loss | (57) | (79)
Total, fair value | 1,507 | 1,485
Total, unrealized loss | (57) | (79)
Corporate bonds |  |
Debt Securities Available for Sale |  |
Less than 12 months, fair value | 0 | 1,229
Less than 12 months, unrealized loss | 0 | (17)
12 months or more, fair value | 4,253 | 4,608
12 months or more, unrealized loss | (191) | (328)
Total, fair value | 4,253 | 5,837
Total, unrealized loss | (191) | (345)
Asset backed securities |  |
Debt Securities Available for Sale |  |
Less than 12 months, fair value | 66,780 | 44,707
Less than 12 months, unrealized loss | (340) | (30)
12 months or more, fair value | 72,002 | 75,734
12 months or more, unrealized loss | (1,901) | (1,208)
Total, fair value | 138,782 | 120,441
Total, unrealized loss | (2,241) | (1,238)
Non-agency collateralized mortgage obligations |  |
Debt Securities Available for Sale |  |
Less than 12 months, fair value | 0 | 0
Less than 12 months, unrealized loss | 0 | 0
12 months or more, fair value | 215,877 | 236,671
12 months or more, unrealized loss | (24,067) | (29,638)
Total, fair value | 215,877 | 236,671
Total, unrealized loss | $ (24,067) | $ (29,638)

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