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Investment Securities (Details) (USD $) | Mar. 31, 2014 | Dec. 31, 2013
--- | --- | ---
Held-to-maturity securities |  |
Amortized Cost | $ 2,400,000 | $ 2,400,000
Estimated Fair Value | 2,400,000 | 2,400,000
Carrying Value | 2,400,000 | 2,400,000
Available-for-sale securities |  |
Amortized Cost | 5,259,440,000 | 5,372,594,000
Gross Unrealized Gains | 66,045,000 | 65,104,000
Gross Unrealized Losses | (102,928,000) | (133,119,000)
Total investment securities | 5,222,557,000 | 5,304,579,000
Estimated Fair Value |  |
Available-for-sale securities |  |
Total investment securities | 5,222,557,000 | 5,304,579,000
Carrying Value |  |
Available-for-sale securities |  |
Total investment securities | 5,222,557,000 | 5,304,579,000
Other securities |  |
Held-to-maturity securities |  |
Amortized Cost | 2,400,000 | 2,400,000
Estimated Fair Value | 2,400,000 | 2,400,000
Carrying Value | 2,400,000 | 2,400,000
Residential mortgage-backed securities |  |
Available-for-sale securities |  |
Amortized Cost | 4,976,280,000 | 5,096,165,000
Gross Unrealized Gains | 52,022,000 | 56,110,000
Gross Unrealized Losses | (95,797,000) | (124,574,000)
Residential mortgage-backed securities | Estimated Fair Value |  |
Available-for-sale securities |  |
Total investment securities | 4,932,505,000 | 5,027,701,000
Residential mortgage-backed securities | Carrying Value |  |
Available-for-sale securities |  |
Total investment securities | 4,932,505,000 | 5,027,701,000
Mortgage-backed securities by Ginnie Mae |  |
Available-for-sale securities |  |
Total investment securities | 1,639,116,000 | 1,799,807,000
Mortgage-backed securities by Fannie Mae and Freddie Mac |  |
Available-for-sale securities |  |
Total investment securities | 3,266,433,000 | 3,200,042,000
Mortgage-backed securities by non-government entities |  |
Available-for-sale securities |  |
Total investment securities | 26,956,000 | 27,852,000
Obligations of states and political subdivisions |  |
Available-for-sale securities |  |
Amortized Cost | 255,085,000 | 248,354,000
Gross Unrealized Gains | 12,780,000 | 8,063,000
Gross Unrealized Losses | (6,740,000) | (8,007,000)
Obligations of states and political subdivisions | Estimated Fair Value |  |
Available-for-sale securities |  |
Total investment securities | 261,125,000 | 248,410,000
Obligations of states and political subdivisions | Carrying Value |  |
Available-for-sale securities |  |
Total investment securities | 261,125,000 | 248,410,000
Equity Securities |  |
Available-for-sale securities |  |
Amortized Cost | 28,075,000 | 28,075,000
Gross Unrealized Gains | 1,243,000 | 931,000
Gross Unrealized Losses | (391,000) | (538,000)
Equity Securities | Estimated Fair Value |  |
Available-for-sale securities |  |
Total investment securities | 28,927,000 | 28,468,000
Equity Securities | Carrying Value |  |
Available-for-sale securities |  |
Total investment securities | $ 28,927,000 | $ 28,468,000

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