| **DERIVATIVES (Offsetting of Financial Assets) (Details) - USD ($) $ in Thousands**                                                                                | Sep. 30, 2019 | Dec. 31, 2018 |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Offsetting Assets [Line Items]**                                                                                                                                 |          |          |
| Gross Amounts of Recognized Assets, Total derivatives subject to a master netting arrangement or similar arrangement                                               | $ 711,200     | $ 515,808     |
| Gross Amounts Offset in the Condensed Consolidated Balance Sheet, Total Derivative Assets                                                                          | 628           | 6,570         |
| Net Amounts of Assets Presented in the Condensed Consolidated Balance Sheet, Total derivatives subject to a master netting arrangement or similar arrangement      | 710,572       | 509,238       |
| Gross Amounts Not Offset in the Condensed Consolidated Balance Sheet, Collateral Received, Total Derivative Assets                                                 | 83,251        | 140,033       |
| Gross Amounts Not Offset in the Condensed Consolidated Balance Sheet, Net Amount, Total derivatives subject to a master netting arrangement or similar arrangement | 627,321       | 369,205       |
| Total derivatives not subject to a master netting arrangement or similar arrangement                                                                               | 5,444         | 2,677         |
| Gross Amounts Not Offset in the Condensed Consolidated Balance Sheet, Collateral Received                                                                          | 2,079         |          |
| Gross Amounts Not Offset in the Condensed Consolidated Balance Sheet, Net Amount                                                                                   | 3,365         | 2,677         |
| Gross Amounts of Recognized Assets, Total Derivative Assets                                                                                                        | 716,644       | 518,485       |
| Net Amounts of Assets Presented in the Condensed Consolidated Balance Sheet, Total Derivative Assets                                                               | 716,016       | 511,915       |
| Gross Amounts Not Offset in the Condensed Consolidated Balance Sheet, Collateral Received, Total Derivative Assets                                                 | 85,330        | 140,033       |
| Gross Amounts Not Offset in the Condensed Consolidated Balance Sheet - Net Amount, Total Derivative Assets                                                         | 630,686       | 371,882       |
| Other derivative activities                                                                                                                                        |          |          |
| **Offsetting Assets [Line Items]**                                                                                                                                 |          |          |
| Gross Amounts of Recognized Assets, Total derivatives subject to a master netting arrangement or similar arrangement                                               | 661,443       | 460,822       |
| Gross Amounts Offset in the Condensed Consolidated Balance Sheet, Total Derivative Assets                                                                          | 628           | 6,570         |
| Net Amounts of Assets Presented in the Condensed Consolidated Balance Sheet, Total derivatives subject to a master netting arrangement or similar arrangement      | 660,815       | 454,252       |
| Gross Amounts Not Offset in the Condensed Consolidated Balance Sheet, Collateral Received, Total Derivative Assets                                                 | 66,181        | 117,582       |
| Gross Amounts Not Offset in the Condensed Consolidated Balance Sheet, Net Amount, Total derivatives subject to a master netting arrangement or similar arrangement | 594,634       | 336,670       |
| Cash flow hedges                                                                                                                                                   |          |          |
| **Offsetting Assets [Line Items]**                                                                                                                                 |          |          |
| Gross Amounts of Recognized Assets, Total derivatives subject to a master netting arrangement or similar arrangement                                               | 49,757        | 54,986        |
| Gross Amounts Offset in the Condensed Consolidated Balance Sheet, Total Derivative Assets                                                                          | 0             | 0             |
| Net Amounts of Assets Presented in the Condensed Consolidated Balance Sheet, Total derivatives subject to a master netting arrangement or similar arrangement      | 49,757        | 54,986        |
| Gross Amounts Not Offset in the Condensed Consolidated Balance Sheet, Collateral Received, Total Derivative Assets                                                 | 17,070        | 22,451        |
| Gross Amounts Not Offset in the Condensed Consolidated Balance Sheet, Net Amount, Total derivatives subject to a master netting arrangement or similar arrangement | $ 32,687      | $ 32,535      |

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Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.
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Fair value, after effects of master netting arrangements, deduction of assets not subject to a master netting arrangement and elected not to be offset, of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, offset against an obligation to return collateral.
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Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets.
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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.
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| - Definition
Fair value, after effects of master netting arrangements, of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset offset against an obligation to return collateral. Includes assets not subject to a master netting arrangement and not elected to be offset.
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