| **COMMITMENTS, CONTINGENCIES, AND GUARANTEES (Loans Sold with Recourse and Commitments to Sell Loans) (Details) - USD ($) $ in Millions** | 6 Months Ended |         |
|-------------------------------------------------------------------------------------------------------------------------------------------|----------------|---------|
||
| **Commitments [Line Items]**                                                                                                              |           |    |
| Retained credit risk, multifamily servicing                                                                                               | $ 30.8         | $ 40.7  |
| Collateral posted                                                                                                                         | 127.3          | 127.6   |
| Residential mortgages [Member]                                                                                                            |           |    |
| **Commitments [Line Items]**                                                                                                              |           |    |
| Loans sold with recourse, maximum exposure                                                                                                | $ 20.5         | 22.1    |
| FNMA [Member] | Multi-family loans [Member]                                                                                               |           |    |
| **Commitments [Line Items]**                                                                                                              |           |    |
| Loans sold with recourse, portion of first credit loss position retained, percent                                                         | 100.00%        |    |
| Recourse and credit enhancement exposure on sold loans [Member]                                                                           |           |    |
| **Commitments [Line Items]**                                                                                                              |           |    |
| Collateral posted                                                                                                                         | $ 0.9          | 0.9     |
| Recourse and credit enhancement exposure on sold loans [Member] | Residential mortgages [Member]                                          |           |    |
| **Commitments [Line Items]**                                                                                                              |           |    |
| Loans sold with recourse, unpaid principal balance                                                                                        | 50.9           | 55.8    |
| Recourse and credit enhancement exposure on sold loans [Member] | FNMA [Member] | Multi-family loans [Member]                             |           |    |
| **Commitments [Line Items]**                                                                                                              |           |    |
| Loans sold with recourse, unpaid principal balance                                                                                        | 2,100.0        | 2,600.0 |
| Value of underlying collateral                                                                                                            | $ 149.6        | $ 152.8 |
| Commitments to sell loans [Member]                                                                                                        |           |    |
| **Commitments [Line Items]**                                                                                                              |           |    |
| Forward contracts maturity period (less than one year)                                                                                    | 1 year         |    |

| X                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Commitments
+ References
No definition available.
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| X                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Derivative, Maturity Period
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                           |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Portion (in percent) of first credit loss position on loans sold with recourse retained.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Unpaid principal balance of loans sold with recourse at period end.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                   |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Loans Sold with Recourse, Maximum Exposure
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                      |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Retained Credit Risk, Multifamily Servicing
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4H -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624258-113959
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248
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| X                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                       |
|---------------------------------------------------------------------------------------------------------------------------------------------------------|
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