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Securities - Schedule of Changes in Equity Securities Without Readily Determinable Fair Values (Detail) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
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Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Equity Securities, FV-NI and without Readily Determinable Fair Value [Abstract] |  |  |  |
Beginning balance | $ 533,749 | $ 371,123 | $ 416,750 | $ 394,035
Acquisition of HTLF | (19,675) |  | 103,211 |
Purchases of securities | 34,919 | 33,397 | 83,749 | 45,154
Observable upward price adjustments | 3,462 | 2,552 | 13,895 | 15,740
Observable downward price adjustments | (653) | (268) | (9,228) | (6,042)
Sales of securities and other activity | (10,783) | (7,032) | (67,358) | (49,115)
Ending balance | $ 541,019 | $ 399,772 | $ 541,019 | $ 399,772

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- Definition Equity securities without readily determinable fair value, purchases of securities. + References No definition available. + Details
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- Definition Amount of investment in equity security without readily determinable fair value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 321 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479536/321-10-50-3 + Details
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- Definition Amount of loss from downward price adjustment on investment in equity security without readily determinable fair value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 321 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479536/321-10-50-3 + Details
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- Definition Amount of gain from upward price adjustment on investment in equity security without readily determinable fair value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 321 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479536/321-10-50-3 + Details
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