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Investment Securities (Schedule Of Investments Within The Available For Sale Portfolio That Had Unrealized Losses) (Details) - USD ($) $ in Thousands | Jun. 30, 2018 | Dec. 31, 2017
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Schedule of Investments [Line Items] |  |
Less than 12 months, Fair Value | $ 3,316,041 | $ 2,514,856
Less than 12 months, Unrealized Losses | (88,730) | (12,243)
12 months or longer, Fair Value | 1,072,711 | 1,164,073
12 months or longer, Unrealized Losses | (59,449) | (35,674)
Total Fair Value | 4,388,752 | 3,678,929
Total Unrealized Losses | (148,179) | (47,917)
U.S. treasuries |  |
Schedule of Investments [Line Items] |  |
Less than 12 months, Fair Value | 98 | 99
Less than 12 months, Unrealized Losses | (2) | (1)
12 months or longer, Fair Value | 0 | 0
12 months or longer, Unrealized Losses | 0 | 0
Total Fair Value | 98 | 99
Total Unrealized Losses | (2) | (1)
Government agency issued MBS |  |
Schedule of Investments [Line Items] |  |
Less than 12 months, Fair Value | 1,937,255 | 1,455,476
Less than 12 months, Unrealized Losses | (57,182) | (4,738)
12 months or longer, Fair Value | 317,784 | 331,900
12 months or longer, Unrealized Losses | (17,376) | (8,866)
Total Fair Value | 2,255,039 | 1,787,376
Total Unrealized Losses | (74,558) | (13,604)
Government agency issued CMO |  |
Schedule of Investments [Line Items] |  |
Less than 12 months, Fair Value | 1,278,976 | 1,043,987
Less than 12 months, Unrealized Losses | (30,862) | (7,464)
12 months or longer, Fair Value | 754,927 | 832,173
12 months or longer, Unrealized Losses | (42,073) | (26,808)
Total Fair Value | 2,033,903 | 1,876,160
Total Unrealized Losses | (72,935) | (34,272)
Other U.S. government agencies |  |
Schedule of Investments [Line Items] |  |
Less than 12 months, Fair Value | 54,402 |
Less than 12 months, Unrealized Losses | (395) |
12 months or longer, Fair Value | 0 |
12 months or longer, Unrealized Losses | 0 |
Total Fair Value | 54,402 |
Total Unrealized Losses | (395) |
Corporates and other debt |  |
Schedule of Investments [Line Items] |  |
Less than 12 months, Fair Value | 40,586 |
Less than 12 months, Unrealized Losses | (259) |
12 months or longer, Fair Value | 0 |
12 months or longer, Unrealized Losses | 0 |
Total Fair Value | 40,586 |
Total Unrealized Losses | (259) |
States and municipalities |  |
Schedule of Investments [Line Items] |  |
Less than 12 months, Fair Value | 4,724 |
Less than 12 months, Unrealized Losses | (30) |
12 months or longer, Fair Value | 0 |
12 months or longer, Unrealized Losses | 0 |
Total Fair Value | 4,724 |
Total Unrealized Losses | $ (30) |
Corporates and other debt |  |
Schedule of Investments [Line Items] |  |
Less than 12 months, Fair Value |  | 15,294
Less than 12 months, Unrealized Losses |  | (40)
12 months or longer, Fair Value |  | 0
12 months or longer, Unrealized Losses |  | 0
Total Fair Value |  | 15,294
Total Unrealized Losses |  | $ (40)

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