| **INVESTMENT SECURITIES (Gross Unrealized Loss and Fair Value of Securities Available for Sale) (Details) - USD ($) $ in Thousands** | Dec. 31, 2015 | Dec. 31, 2014 |
|--------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Fair Value**                                                                                                                       |          |          |
| Less than 12 months                                                                                                                  | $ 10,139,369  | $ 2,622,575   |
| 12 months or longer                                                                                                                  | 3,420,300     | 4,934,027     |
| Total                                                                                                                                | 13,559,669    | 7,556,602     |
| **Unrealized Losses**                                                                                                                |          |          |
| Less than 12 months                                                                                                                  | (67,205)      | (12,187)      |
| 12 months or longer                                                                                                                  | (151,339)     | (173,192)     |
| Total                                                                                                                                | (218,544)     | (185,379)     |
| U.S. Treasury securities                                                                                                             |          |          |
| **Fair Value**                                                                                                                       |          |          |
| Less than 12 months                                                                                                                  | 2,243,343     | 298,914       |
| 12 months or longer                                                                                                                  | 0             | 0             |
| Total                                                                                                                                | 2,243,343     | 298,914       |
| **Unrealized Losses**                                                                                                                |          |          |
| Less than 12 months                                                                                                                  | (5,681)       | (56)          |
| 12 months or longer                                                                                                                  | 0             | 0             |
| Total                                                                                                                                | (5,681)       | (56)          |
| Corporate debt securities                                                                                                            |          |          |
| **Fair Value**                                                                                                                       |          |          |
| Less than 12 months                                                                                                                  | 775,366       | 538,108       |
| 12 months or longer                                                                                                                  | 152,486       | 214,852       |
| Total                                                                                                                                | 927,852       | 752,960       |
| **Unrealized Losses**                                                                                                                |          |          |
| Less than 12 months                                                                                                                  | (5,269)       | (3,262)       |
| 12 months or longer                                                                                                                  | (5,979)       | (3,648)       |
| Total                                                                                                                                | (11,248)      | (6,910)       |
| Asset-backed securities                                                                                                              |          |          |
| **Fair Value**                                                                                                                       |          |          |
| Less than 12 months                                                                                                                  | 300,869       | 632,936       |
| 12 months or longer                                                                                                                  | 35,126        | 424,333       |
| Total                                                                                                                                | 335,995       | 1,057,269     |
| **Unrealized Losses**                                                                                                                |          |          |
| Less than 12 months                                                                                                                  | (1,083)       | (1,437)       |
| 12 months or longer                                                                                                                  | (411)         | (3,154)       |
| Total                                                                                                                                | (1,494)       | (4,591)       |
| Equity securities                                                                                                                    |          |          |
| **Fair Value**                                                                                                                       |          |          |
| Less than 12 months                                                                                                                  | 596           | 55            |
| 12 months or longer                                                                                                                  | 9,748         | 9,879         |
| Total                                                                                                                                | 10,344        | 9,934         |
| **Unrealized Losses**                                                                                                                |          |          |
| Less than 12 months                                                                                                                  | (7)           | 0             |
| 12 months or longer                                                                                                                  | (401)         | (279)         |
| Total                                                                                                                                | (408)         | (279)         |
| State and municipal securities                                                                                                       |          |          |
| **Fair Value**                                                                                                                       |          |          |
| Less than 12 months                                                                                                                  | 15,665        | 45,128        |
| 12 months or longer                                                                                                                  | 26,024        | 192,091       |
| Total                                                                                                                                | 41,689        | 237,219       |
| **Unrealized Losses**                                                                                                                |          |          |
| Less than 12 months                                                                                                                  | (119)         | (90)          |
| 12 months or longer                                                                                                                  | (313)         | (2,295)       |
| Total                                                                                                                                | (432)         | (2,385)       |
| U.S. government agencies - Residential                                                                                               |          |          |
| **Fair Value**                                                                                                                       |          |          |
| Less than 12 months                                                                                                                  | 1,670,150     | 415,731       |
| 12 months or longer                                                                                                                  | 954,916       | 1,348,908     |
| Total                                                                                                                                | 2,625,066     | 1,764,639     |
| **Unrealized Losses**                                                                                                                |          |          |
| Less than 12 months                                                                                                                  | (11,164)      | (2,693)       |
| 12 months or longer                                                                                                                  | (25,349)      | (31,118)      |
| Total                                                                                                                                | (36,513)      | (33,811)      |
| U.S. government agencies - Commercial                                                                                                |          |          |
| **Fair Value**                                                                                                                       |          |          |
| Less than 12 months                                                                                                                  | 367,706       | 281,258       |
| 12 months or longer                                                                                                                  | 114,038       | 136,269       |
| Total                                                                                                                                | 481,744       | 417,527       |
| **Unrealized Losses**                                                                                                                |          |          |
| Less than 12 months                                                                                                                  | (3,382)       | (2,459)       |
| 12 months or longer                                                                                                                  | (3,771)       | (4,727)       |
| Total                                                                                                                                | (7,153)       | (7,186)       |
| FHLMC and FNMA - Residential debt securities                                                                                         |          |          |
| **Fair Value**                                                                                                                       |          |          |
| Less than 12 months                                                                                                                  | 4,650,327     | 399,176       |
| 12 months or longer                                                                                                                  | 2,127,962     | 2,607,695     |
| Total                                                                                                                                | 6,778,289     | 3,006,871     |
| **Unrealized Losses**                                                                                                                |          |          |
| Less than 12 months                                                                                                                  | (38,013)      | (2,019)       |
| 12 months or longer                                                                                                                  | (115,115)     | (127,971)     |
| Total                                                                                                                                | (153,128)     | (129,990)     |
| FHLMC and FNMA - Commercial debt securities                                                                                          |          |          |
| **Fair Value**                                                                                                                       |          |          |
| Less than 12 months                                                                                                                  | 115,347       | 11,269        |
| 12 months or longer                                                                                                                  | 0             | 0             |
| Total                                                                                                                                | 115,347       | 11,269        |
| **Unrealized Losses**                                                                                                                |          |          |
| Less than 12 months                                                                                                                  | (2,487)       | (171)         |
| 12 months or longer                                                                                                                  | 0             | 0             |
| Total                                                                                                                                | $ (2,487)     | $ (171)       |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.
+ References
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.
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| - Definition
This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for less than twelve months.
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