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Investment Securities (Summary Of Available For Sale Investment Securities By Maturity Groupings) (Details) - USD ($) | Mar. 31, 2026 | Dec. 31, 2025
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 9,333,626,000 | $ 9,742,278,000
Fair Value | 8,646,127,000 | 9,095,513,000
U.S. government and federal agency obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 3,147,185,000 | 3,257,561,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost | 422,299,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost | 1,704,983,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost | 913,297,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost | 106,606,000 |
Fair Value | 3,147,293,000 | 3,279,100,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value | 423,185,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value | 1,707,211,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value | 910,616,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value | 106,281,000 |
Government-sponsored enterprise obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 54,599,000 | 54,951,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost | 3,962,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost | 30,816,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost | 19,821,000 |
Fair Value | 43,985,000 | 44,712,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value | 3,737,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value | 26,321,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value | 13,927,000 |
State and municipal obligations [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 705,864,000 | 715,037,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost | 55,782,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost | 428,431,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost | 116,777,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost | 104,874,000 |
Fair Value | 654,824,000 | 664,733,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value | 55,348,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value | 409,208,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value | 103,102,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value | 87,166,000 |
Agency mortgage-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 3,701,146,000 | 3,786,811,000
Fair Value | 3,123,669,000 | 3,223,105,000
Non-Agency Mortgage-Backed Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 446,168,000 | 467,200,000
Fair Value | 414,777,000 | 435,688,000
Asset-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 1,104,943,000 | 1,269,503,000
Fair Value | 1,093,819,000 | 1,262,045,000
Total Mortgage And Asset-Backed Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 5,252,257,000 | 5,523,514,000
Fair Value | 4,632,265,000 | 4,920,838,000
Other debt securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 173,721,000 | 191,215,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost | 8,021,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost | 59,891,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost | 81,872,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost | 23,937,000 |
Fair Value | 167,760,000 | $ 186,130,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value | 7,924,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value | 55,915,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value | 80,151,000 |
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value | $ 23,770,000 |

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