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Investment Securities - Amortized Cost and Fair Value of Available-for-Sale Investment Securities Portfolio (Details) - USD ($) $ in Thousands | Dec. 31, 2025 | Dec. 31, 2024
--- | --- | ---
Available-for-Sale |  |
Amortized Cost | $ 12,059,997 | $ 8,480,508
Unrealized Gains | 83,904 | 6,987
Unrealized Losses | (654,333) | (897,516)
Basis Adjustments | (105,118) | (131,520)
Fair Value | 11,384,450 | 7,458,459
U.S. Treasury |  |
Available-for-Sale |  |
Amortized Cost | 269,313 | 261,421
Unrealized Gains | 90 | 67
Unrealized Losses | (7,615) | (12,659)
Basis Adjustments | (47,244) | (49,816)
Fair Value | 214,544 | 199,013
U.S. government-sponsored entities and agencies |  |
Available-for-Sale |  |
Amortized Cost | 1,567,036 | 1,521,610
Unrealized Gains | 402 | 7
Unrealized Losses | (134,795) | (181,360)
Basis Adjustments | (60,251) | (82,351)
Fair Value | 1,372,392 | 1,257,906
Mortgage-backed securities |  |
Available-for-Sale |  |
Amortized Cost | 9,575,241 | 5,861,067
Unrealized Gains | 79,999 | 6,005
Unrealized Losses | (487,205) | (662,181)
Basis Adjustments | 0 | 0
Fair Value | 9,168,035 | 5,204,891
States and political subdivisions |  |
Available-for-Sale |  |
Amortized Cost | 438,642 | 510,630
Unrealized Gains | 2,275 | 148
Unrealized Losses | (17,286) | (25,881)
Basis Adjustments | 2,377 | 647
Fair Value | 426,008 | 485,544
Pooled trust preferred securities |  |
Available-for-Sale |  |
Amortized Cost | 13,819 | 13,807
Unrealized Gains | 0 | 0
Unrealized Losses | (2,085) | (2,485)
Basis Adjustments | 0 | 0
Fair Value | 11,734 | 11,322
Other securities |  |
Available-for-Sale |  |
Amortized Cost | 195,946 | 311,973
Unrealized Gains | 1,138 | 760
Unrealized Losses | (5,347) | (12,950)
Basis Adjustments | 0 | 0
Fair Value | $ 191,737 | $ 299,783

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- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-2 + Details
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- Definition Amortized cost excluding accrued interest, before allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479130/326-30-45-1 + Details
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