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Investment Securities Available for Sale (Schedule Of Unrealized Loss On Investments) (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
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Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 Months, Fair Value | $ 1,379,662 | $ 891,914
Less than 12 Months, Gross Unrealized Losses | (16,669) | (2,468)
12 Months or Longer, Fair Value | 0 | 5,309
12 Months or Longer, Gross Unrealized Losses | 0 | (38)
Total, Fair Value | 1,379,662 | 897,223
Total, Gross Unrealized Losses | (16,669) | (2,506)
Gross Unrealized Gains | 177,243 | 133,385
Gross Unrealized Losses | (16,669) | (2,506)
Investment securities available for sale, at fair value | 7,962,438 | 6,778,670
Debt Securities, Available-for-sale, Amortized Cost | 7,801,864 | 6,647,791
Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization | 463,959 | 493,940
U.S. Treasury securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | 0
Investment securities available for sale, at fair value | 20,257 | 19,855
Debt Securities, Available-for-sale, Amortized Cost | 20,257 | 19,855
U.S. Government agency securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Gross Unrealized Gains | 2,682 | 1,042
Gross Unrealized Losses | 0 | 0
Investment securities available for sale, at fair value | 82,320 | 36,541
Debt Securities, Available-for-sale, Amortized Cost | 79,638 | 35,499
Mortgage-backed securities issued by U.S. Government agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 Months, Fair Value | 566,896 | 19,543
Less than 12 Months, Gross Unrealized Losses | (5,925) | (70)
12 Months or Longer, Fair Value | 0 | 355
12 Months or Longer, Gross Unrealized Losses | 0 | (2)
Total, Fair Value | 566,896 | 19,898
Total, Gross Unrealized Losses | (5,925) | (72)
Gross Unrealized Gains | 7,930 | 560
Gross Unrealized Losses | (5,925) | (72)
Investment securities available for sale, at fair value | 1,218,017 | 56,816
Debt Securities, Available-for-sale, Amortized Cost | 1,216,012 | 56,328
Mortgage-backed securities issued by U.S. Government sponsored enterprises |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 Months, Fair Value |  | 768,040
Less than 12 Months, Gross Unrealized Losses |  | (2,076)
12 Months or Longer, Fair Value |  | 0
12 Months or Longer, Gross Unrealized Losses |  | 0
Total, Fair Value |  | 768,040
Total, Gross Unrealized Losses |  | (2,076)
Gross Unrealized Gains | 134,188 | 103,495
Gross Unrealized Losses | 0 | (2,076)
Investment securities available for sale, at fair value | 5,000,046 | 5,180,815
Debt Securities, Available-for-sale, Amortized Cost | 4,865,858 | 5,079,396
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 Months, Fair Value | 803,429 | 57,670
Less than 12 Months, Gross Unrealized Losses | (10,576) | (204)
12 Months or Longer, Fair Value | 0 | 0
12 Months or Longer, Gross Unrealized Losses | 0 | 0
Total, Fair Value | 803,429 | 57,670
Total, Gross Unrealized Losses | (10,576) | (204)
Gross Unrealized Gains | 15,309 | 7,349
Gross Unrealized Losses | (10,576) | (204)
Investment securities available for sale, at fair value | 1,250,377 | 636,851
Debt Securities, Available-for-sale, Amortized Cost | 1,245,644 | 629,706
Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises |  |
Debt Securities, Available-for-sale [Line Items] |  |
Gross Unrealized Gains | 16,677 | 14,301
Gross Unrealized Losses | 0 | 0
Investment securities available for sale, at fair value | 370,921 | 371,592
Debt Securities, Available-for-sale, Amortized Cost | 354,244 | 357,291
State and municipal securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Gross Unrealized Gains |  | 6
Gross Unrealized Losses |  | 0
Investment securities available for sale, at fair value |  | 2,075
Debt Securities, Available-for-sale, Amortized Cost |  | 2,069
Asset-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 Months, Fair Value |  | 37,156
Less than 12 Months, Gross Unrealized Losses |  | (116)
12 Months or Longer, Fair Value |  | 4,954
12 Months or Longer, Gross Unrealized Losses |  | (36)
Total, Fair Value |  | 42,110
Total, Gross Unrealized Losses |  | (152)
Gross Unrealized Gains |  | 4,315
Gross Unrealized Losses |  | (152)
Investment securities available for sale, at fair value |  | 327,400
Debt Securities, Available-for-sale, Amortized Cost |  | 323,237
Corporate debt securities and other debt securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 Months, Fair Value | 9,337 | 9,505
Less than 12 Months, Gross Unrealized Losses | (168) | (2)
12 Months or Longer, Fair Value | 0 | 0
12 Months or Longer, Gross Unrealized Losses | 0 | 0
Total, Fair Value | 9,337 | 9,505
Total, Gross Unrealized Losses | (168) | (2)
Gross Unrealized Gains | 457 | 2,317
Gross Unrealized Losses | (168) | (2)
Investment securities available for sale, at fair value | 20,500 | 146,725
Debt Securities, Available-for-sale, Amortized Cost | $ 20,211 | $ 144,410

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