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INVESTMENT SECURITIES (Details) (USD $) | Sep. 30, 2014 | Dec. 31, 2013 | Sep. 30, 2013 | Dec. 31, 2012
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Schedule of Available-for-sale Securities |  |  |  |  |  |
Investment securities available-for-sale, amortized cost | $ 2,596,823,000 |  | $ 2,786,490,000 |  |  |
Gross Unrealized Gains | 19,930,000 |  | 12,203,000 |  |  |
Gross Unrealized Losses | (24,086,000) |  | (64,896,000) |  |  |
Fair Value | 2,592,667,000 |  | 2,733,797,000 |  |  |
OTTI credit losses | 115,500,000 |  | 115,500,000 |  | 115,500,000 | 115,500,000
U.S. Treasury securities |  |  |  |  |  |
Schedule of Available-for-sale Securities |  |  |  |  |  |
Investment securities available-for-sale, amortized cost | 605,672,000 |  | 495,053,000 |  |  |
Gross Unrealized Gains | 328,000 |  | 201,000 |  |  |
Gross Unrealized Losses | (2,353,000) |  | (3,622,000) |  |  |
Fair Value | 603,647,000 |  | 491,632,000 |  |  |
U.S. government agency and U.S. government sponsored enterprise debt securities |  |  |  |  |  |
Schedule of Available-for-sale Securities |  |  |  |  |  |
Investment securities available-for-sale, amortized cost | 416,746,000 |  | 406,807,000 |  |  |
Gross Unrealized Gains | 522,000 |  | 242,000 |  |  |
Gross Unrealized Losses | (4,287,000) |  | (12,726,000) |  |  |
Fair Value | 412,981,000 |  | 394,323,000 |  |  |
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities |  |  |  |  |  |
Schedule of Available-for-sale Securities |  |  |  |  |  |
Investment securities available-for-sale, amortized cost | 125,933,000 |  | 182,257,000 |  |  |
Gross Unrealized Gains | 1,188,000 |  | 1,062,000 |  |  |
Gross Unrealized Losses | (1,554,000) |  | (4,449,000) |  |  |
Fair Value | 125,567,000 |  | 178,870,000 |  |  |
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities |  |  |  |  |  |
Schedule of Available-for-sale Securities |  |  |  |  |  |
Investment securities available-for-sale, amortized cost | 757,637,000 |  | 892,435,000 |  |  |
Gross Unrealized Gains | 8,003,000 |  | 7,729,000 |  |  |
Gross Unrealized Losses | (8,058,000) |  | (14,927,000) |  |  |
Fair Value | 757,582,000 |  | 885,237,000 |  |  |
Municipal securities |  |  |  |  |  |
Schedule of Available-for-sale Securities |  |  |  |  |  |
Investment securities available-for-sale, amortized cost | 293,148,000 |  | 297,390,000 |  |  |
Gross Unrealized Gains | 5,984,000 |  | 1,122,000 |  |  |
Gross Unrealized Losses | (2,535,000) |  | (17,533,000) |  |  |
Fair Value | 296,597,000 |  | 280,979,000 |  |  |
Other residential mortgage-backed securities: | Investment grade |  |  |  |  |  |
Schedule of Available-for-sale Securities |  |  |  |  |  |
Investment securities available-for-sale, amortized cost | 54,949,000 | [1] | 48,129,000 | [1] |  |
Gross Unrealized Gains | 665,000 | [1] |  |  |  |
Gross Unrealized Losses | (356,000) | [1] | (1,802,000) | [1] |  |
Fair Value | 55,258,000 | [1] | 46,327,000 | [1] |  |
Other commercial mortgage-backed securities: | Investment grade |  |  |  |  |  |
Schedule of Available-for-sale Securities |  |  |  |  |  |
Investment securities available-for-sale, amortized cost | 51,000,000 | [1] | 51,000,000 | [1] |  |
Gross Unrealized Gains | 127,000 | [1] | 617,000 | [1] |  |
Fair Value | 51,127,000 | [1] | 51,617,000 | [1] |  |
Corporate debt securities | Investment grade |  |  |  |  |  |
Schedule of Available-for-sale Securities |  |  |  |  |  |
Investment securities available-for-sale, amortized cost | 211,143,000 | [1] | 312,726,000 | [1] |  |
Gross Unrealized Gains | 1,127,000 | [1] | 613,000 | [1] |  |
Gross Unrealized Losses | (1,445,000) | [1] | (3,344,000) | [1] |  |
Fair Value | 210,825,000 | [1] | 309,995,000 | [1] |  |
Corporate debt securities | Non-investment grade |  |  |  |  |  |
Schedule of Available-for-sale Securities |  |  |  |  |  |
Investment securities available-for-sale, amortized cost | 19,937,000 | [1] | 20,668,000 | [1] |  |
Gross Unrealized Gains | 802,000 | [1] | 62,000 | [1] |  |
Gross Unrealized Losses | (2,963,000) | [1] | (5,629,000) | [1] |  |
Fair Value | 17,776,000 | [1] | 15,101,000 | [1] |  |
Other securities |  |  |  |  |  |
Schedule of Available-for-sale Securities |  |  |  |  |  |
Investment securities available-for-sale, amortized cost | 60,658,000 |  | 80,025,000 |  |  |
Gross Unrealized Gains | 1,184,000 |  | 555,000 |  |  |
Gross Unrealized Losses | (535,000) |  | (864,000) |  |  |
Fair Value | $ 61,307,000 |  | $ 79,716,000 |  |  |
[1] | Investment securities rated BBB- or higher by S&P or Baa3 or higher by Moody's are considered investment grade. Conversely, investment securities rated lower than BBB- by S&P or lower than Baa3 by Moody's are considered non-investment grade.

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