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Investment Securities (Details 3) (USD $) In Thousands, unless otherwise specified | Sep. 30, 2013 | Dec. 31, 2012
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Available for sale: |  |
Fair value, less than 12 months | $ 2,661,685 | $ 743,609
Unrealized losses, less than 12 months | (87,343) | (5,590)
Fair value, 12 months or more | 106,491 | 43,353
Unrealized losses, 12 months or more | (15,245) | (12,254)
Fair value, total | 2,768,176 | 786,962
Unrealized losses, total | (102,588) | (17,844)
Residential mortgage-backed securities |  |
Available for sale: |  |
Fair value, less than 12 months | 2,599,415 | 738,492
Unrealized losses, less than 12 months | (84,205) | (5,476)
Fair value, 12 months or more | 94,376 | 32,860
Unrealized losses, 12 months or more | (11,376) | (10,557)
Fair value, total | 2,693,791 | 771,352
Unrealized losses, total | (95,581) | (16,033)
Obligations of states and political subdivisions |  |
Available for sale: |  |
Fair value, less than 12 months | 51,800 | 5,117
Unrealized losses, less than 12 months | (2,859) | (114)
Fair value, 12 months or more | 12,044 | 10,437
Unrealized losses, 12 months or more | (3,865) | (1,677)
Fair value, total | 63,844 | 15,554
Unrealized losses, total | (6,724) | (1,791)
Equity Securities |  |
Available for sale: |  |
Fair value, less than 12 months | 10,470 |
Unrealized losses, less than 12 months | (279) |
Fair value, 12 months or more | 71 | 56
Unrealized losses, 12 months or more | (4) | (20)
Fair value, total | 10,541 | 56
Unrealized losses, total | $ (283) | $ (20)

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