| **LOANS AND ALLOWANCE FOR CREDIT LOSSES (As Restated) (Lending Asset Quality Indicators) (Details) - USD ($) $ in Thousands** | Dec. 31, 2015 | Dec. 31, 2014 |
|-------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | $ 40,712,119  | $ 36,641,277  |
| Pass                                                                                                                          |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 38,673,364    | 35,042,598    |
| Special Mention                                                                                                               |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 1,043,286     | 655,721       |
| Substandard                                                                                                                   |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 926,537       | 853,473       |
| Doubtful                                                                                                                      |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 68,932        | 89,485        |
| Commercial and industrial loans                                                                                               |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 19,874,233    | 17,111,922    |
| Commercial and industrial loans | Pass                                                                                        |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 18,881,150    | 16,495,836    |
| Commercial and industrial loans | Special Mention                                                                             |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 492,128       | 237,331       |
| Commercial and industrial loans | Substandard                                                                                 |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 467,983       | 358,782       |
| Commercial and industrial loans | Doubtful                                                                                    |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 32,972        | 19,973        |
| Multifamily                                                                                                                   |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 9,438,463     | 8,705,890     |
| Multifamily | Pass                                                                                                            |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 9,114,466     | 8,533,427     |
| Multifamily | Special Mention                                                                                                 |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 249,165       | 131,677       |
| Multifamily | Substandard                                                                                                     |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 74,410        | 40,355        |
| Multifamily | Doubtful                                                                                                        |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 422           | 431           |
| Remaining commercial                                                                                                          |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 2,676,506     | 2,084,232     |
| Remaining commercial | Pass                                                                                                   |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 2,631,935     | 2,064,947     |
| Remaining commercial | Special Mention                                                                                        |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 28,686        | 8,475         |
| Remaining commercial | Substandard                                                                                            |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 15,601        | 10,311        |
| Remaining commercial | Doubtful                                                                                               |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 284           | 499           |
| Commercial                                                                                                                    |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 40,625,720    | 36,622,183    |
| Commercial | Corporate banking                                                                                                |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 2,949,089     | 3,218,150     |
| Commercial | Corporate banking | Pass                                                                                         |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 2,627,159     | 2,910,957     |
| Commercial | Corporate banking | Special Mention                                                                              |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 99,090        | 83,122        |
| Commercial | Corporate banking | Substandard                                                                                  |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 208,785       | 192,911       |
| Commercial | Corporate banking | Doubtful                                                                                     |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 14,055        | 31,160        |
| Commercial | Middle market commercial real estate                                                                             |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 4,223,359     | 3,743,099     |
| Commercial | Middle market commercial real estate | Pass                                                                      |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 4,055,623     | 3,472,448     |
| Commercial | Middle market commercial real estate | Special Mention                                                           |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 29,620        | 61,166        |
| Commercial | Middle market commercial real estate | Substandard                                                               |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 117,571       | 174,882       |
| Commercial | Middle market commercial real estate | Doubtful                                                                  |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 20,545        | 34,603        |
| Commercial | Santander real estate capital                                                                                    |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 1,550,469     | 1,777,984     |
| Commercial | Santander real estate capital | Pass                                                                             |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 1,363,031     | 1,564,983     |
| Commercial | Santander real estate capital | Special Mention                                                                  |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 144,597       | 133,950       |
| Commercial | Santander real estate capital | Substandard                                                                      |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 42,187        | 76,232        |
| Commercial | Santander real estate capital | Doubtful                                                                         |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 654           | 2,819         |
| Commercial | Commercial and industrial loans                                                                                  |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 19,787,834    | 17,092,828    |
| Commercial | Multifamily                                                                                                      |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | 9,438,463     | 8,705,890     |
| Commercial | Remaining commercial                                                                                             |          |          |
| **Financing Receivable, Recorded Investment [Line Items]**                                                                    |          |          |
| Commercial loans                                                                                                              | $ 2,676,506   | $ 2,084,232   |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Reflects the net carrying amount of commercial loans and leases held in portfolio, after deducting deferred income, but before deducting the allowance for losses on commercial loans and leases.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5074-111524
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