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Investment Securities (Schedule Of Fair Value And Unrealized Losses Of Securities) (Details) - USD ($) $ in Thousands | Mar. 31, 2024 | Dec. 31, 2023
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Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | $ 4,495,441 | $ 1,292,794
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (57,341) | (12,009)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 2,755,606 | 2,809,244
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (510,546) | (476,099)
Debt Securities, Available-for-sale, Unrealized Loss Position | 7,251,047 | 4,102,038
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss | (567,887) | (488,108)
U.S. Treasury and agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 338,230 | 99,898
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (3,305) | (1,074)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 816,265 | 822,245
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (82,674) | (77,800)
Debt Securities, Available-for-sale, Unrealized Loss Position | 1,154,495 | 922,143
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss | (85,979) | (78,874)
Obligations of states and political subdivisions |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 297,204 | 103,256
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (2,464) | (580)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 182,355 | 169,231
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (22,685) | (21,030)
Debt Securities, Available-for-sale, Unrealized Loss Position | 479,559 | 272,487
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss | (25,149) | (21,610)
Mortgage-backed securities and collateralized mortgage obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 3,860,007 | 1,089,640
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (51,572) | (10,355)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 1,756,986 | 1,817,768
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (405,187) | (377,269)
Debt Securities, Available-for-sale, Unrealized Loss Position | 5,616,993 | 2,907,408
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss | $ (456,759) | $ (387,624)

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