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INVESTMENT SECURITIES (Details) - USD ($) $ in Thousands | Mar. 31, 2016 | Dec. 31, 2015
--- | --- | ---
Schedule of Available-for-sale Securities |  |
Amortized Cost | $ 3,193,553 | $ 3,783,829
Gross Unrealized Gains | 21,206 | 11,744
Gross Unrealized Losses | (9,521) | (22,347)
Available-for-sale investment securities, at fair value | 3,205,238 | 3,773,226
Schedule of Held-to-maturity Securities |  |
Amortized Cost | 160,135 | 0
Fair Value | 160,135 | 0
Investment Securities |  |
Amortized Cost | 3,353,688 |
Gross Unrealized Gains | 21,206 |
Gross Unrealized Losses | (9,521) |
Fair Value | 3,365,373 |
U.S. Treasury securities |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 514,827 | 1,002,874
Gross Unrealized Gains | 2,002 | 33
Gross Unrealized Losses | (74) | (4,392)
Available-for-sale investment securities, at fair value | 516,755 | 998,515
U.S. government agency and U.S. government sponsored enterprise debt securities |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 787,846 | 771,288
Gross Unrealized Gains | 1,671 | 555
Gross Unrealized Losses | (582) | (2,994)
Available-for-sale investment securities, at fair value | 788,935 | 768,849
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 325,071 | 354,418
Gross Unrealized Gains | 3,132 | 268
Gross Unrealized Losses | (1,216) | (3,024)
Available-for-sale investment securities, at fair value | 326,987 | 351,662
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 927,989 | 996,255
Gross Unrealized Gains | 9,421 | 7,542
Gross Unrealized Losses | (2,311) | (6,401)
Available-for-sale investment securities, at fair value | 935,099 | 997,396
Municipal securities |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 156,327 | 173,785
Gross Unrealized Gains | 3,254 | 2,657
Gross Unrealized Losses | (155) | (793)
Available-for-sale investment securities, at fair value | 159,426 | 175,649
Non-agency residential mortgage-backed securities | Investment grade |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 58,960 | 62,133
Gross Unrealized Gains | 1,015 | 433
Gross Unrealized Losses | (76) | (173)
Available-for-sale investment securities, at fair value | 59,899 | 62,393
Corporate debt securities | Investment grade |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 368,206 | 366,921
Gross Unrealized Gains | 212 | 132
Gross Unrealized Losses | (2,513) | (2,340)
Available-for-sale investment securities, at fair value | 365,905 | 364,713
Corporate debt securities | Non-investment grade |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 10,191 | 11,491
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (2,267) | (1,849)
Available-for-sale investment securities, at fair value | 7,924 | 9,642
Other securities |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 44,136 | 44,664
Gross Unrealized Gains | 499 | 124
Gross Unrealized Losses | (327) | (381)
Available-for-sale investment securities, at fair value | 44,308 | $ 44,407
Non-agency commercial mortgage-backed security |  |
Schedule of Held-to-maturity Securities |  |
Amortized Cost | 160,135 |
Gross Unrealized Gains | 0 |
Gross Unrealized Losses | 0 |
Fair Value | $ 160,135 |

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