| **BORROWINGS (Santander Bank) (Details) (USD $)In Thousands, unless otherwise specified**                                                                                                                                    |              |              |              |             |           |           |           |     | 1 Months Ended |     |           |         |         |         |         |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------|--------------|--------------|-------------|-----------|-----------|-----------|-----|----------------|-----|-----------|---------|---------|---------|---------|
||
| **Debt Instrument [Line Items]**                                                                                                                                                                                             |         |         |         |        |      |      |      |     |           |     |      |    |    |    |    |   |   |
| Subordinated debentures, Balance                                                                                                                                                                                             |         |         |         |        | $ 497,670 | $ 497,427 |      |     |           |     |      |    |    |    |    |   |   |
| FHLB advances, maturing through August 2018, Balance                                                                                                                                                                         |         |         |         |        |      |      | 9,593,309 | [1] | 8,952,012      | [1] | 1,700,000 |    |    |    |    |   |   |
| Subordinated term loan, Balance                                                                                                                                                                                              |         |         |         |        |      |      |      |     |           |     |      | 145,279 | 150,273 |    |    | 34,674 | 35,491 |
| REIT preferred, due May 2020, Balance                                                                                                                                                                                        |         |         |         |        |      |      |      |     |           |     |      |    |    | 152,666 | 151,918 |   |   |
| Total borrowings and other debt obligations                                                                                                                                                                                  | $ 38,213,650 | $ 12,376,624 | $ 10,423,598 | $ 9,787,121 |      |      |      |     |           |     |      |    |    |    |    |   |   |
| Effective Rate                                                                                                                                                                                                               |         |         | 3.26%        | 3.87%       | 8.91%     | 8.91%     | 2.74%     | [1] | 3.36%          | [1] |      | 6.00%   | 6.06%   | 13.70%  | 13.83%  | 7.77% | 7.78% |
| Stated Rate                                                                                                                                                                                                                  |         |         |         |        | 8.75%     |      | 3.43%     |     | 5.39%          |     |      |    |    |    |    |   |   |
| Debt maturity, extended term                                                                                                                                                                                                 |         |         |         |        |      |      |      |     |           |     | 2 years   |    |    |    |    |   |   |
|                                                                                                                                                                                                                              |
| [1]In February 2014, the Company restructured $1.7 billion of FHLB advances and extended their maturities by two years. The average rate of these borrowings decreased from 5.39% to 3.43% as a result of the restructuring. |

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Borrowings and other debt obligations.
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| - Definition
Debt Instrument, Maturity Period, Extension
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Issuance of Stock, Subsidiary
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| - Definition
Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.
+ References
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| - Definition
Contractual interest rate for funds borrowed, under the debt agreement.
+ References
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| - Definition
Including both current and noncurrent portions, Federal Home Loan Bank borrowings initially due beyond one year or beyond the normal operating cycle if longer.
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Including the current and noncurrent portions, aggregate carrying value as of the balance sheet date of loans payable (with maturities initially due after one year or beyond the operating cycle if longer).
+ References
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.
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