| **DEPOSITS AND OTHER CUSTOMER ACCOUNTS (Summary of Deposits and Other Customer Accounts) (Details) - USD ($) $ in Thousands** | Sep. 30, 2016 | Dec. 31, 2015 |
|-------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Deposits [Abstract]**                                                                                                       |          |          |
| Interest-bearing demand deposits                                                                                              | $ 10,207,447  | $ 11,665,596  |
| Interest-bearing demand deposits (as a percent)                                                                               | 15.10%        | 17.80%        |
| Non-interest-bearing demand deposits                                                                                          | $ 15,592,290  | $ 12,915,025  |
| Non-interest-bearing demand deposits (as a percent)                                                                           | 23.00%        | 19.70%        |
| Savings                                                                                                                       | $ 6,005,579   | $ 6,025,358   |
| Savings (as a percent)                                                                                                        | 8.90%         | 9.10%         |
| Customer repurchase accounts                                                                                                  | $ 919,158     | $ 896,736     |
| Customer repurchase accounts (as a percent)                                                                                   | 1.40%         | 1.40%         |
| Money market                                                                                                                  | $ 25,353,203  | $ 24,437,346  |
| Money market (as a percent)                                                                                                   | 37.40%        | 37.30%        |
| Certificates of deposit                                                                                                       | $ 9,626,448   | $ 9,643,369   |
| Certificates of deposit (as a percent)                                                                                        | 14.20%        | 14.70%        |
| Total Deposits                                                                                                                | $ 67,704,125  | $ 65,583,430  |
| Total Deposits (as a percent)                                                                                                 | 100.00%       | 100.00%       |
| Foreign deposits                                                                                                              | $ 646,500     | $ 565,000     |

| X                                                                                                                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Deposits, Customer Repurchase Accounts
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No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of Interest-Bearing Deposit Liabilities to Deposits, Customer Repurchase Accounts
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No definition available.
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| X                                                                                                                                                                                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of Interest-bearing Deposit Liabilities to Deposit
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of Interest-bearing Deposit Liabilities to Deposits, Certificates of Deposit
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No definition available.
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| X                                                                                                                                                                                                                                                                                                                 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of Interest-bearing Deposit Liabilities to Deposits, Demand
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No definition available.
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| X                                                                                                                                                                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of Interest-bearing Deposit Liabilities to Deposits, Money Market
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No definition available.
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| X                                                                                                                                                                                                                                                                                                                   |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of Interest-bearing Deposit Liabilities to Deposits, Savings
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No definition available.
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| X                                                                                                                                                                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of Noninterest-bearing Deposit Liabilities to Deposits, Demand
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.
+ References
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| X                                                                                                                                                                                          |
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The aggregate of all foreign interest-bearing and noninterest-bearing deposit liabilities.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of deposits in accounts that offer many of the same services as checking accounts although transactions may be somewhat more limited, share some of the characteristics of a money market fund and are insured by the Federal government, also known as money market accounts.
+ References
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of interest bearing deposits with no stated maturity, which may include passbook and statement savings accounts and money-market deposit accounts (MMDAs).
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The aggregate of all domestic and foreign interest-bearing deposit liabilities.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The aggregate amount of all domestic and foreign noninterest-bearing deposits liabilities held by the entity.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of time deposit liabilities, including certificates of deposit.
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