| **ACCUMULATED OTHER COMPREHENSIVE INCOME / (LOSS) (Details) - USD ($) $ in Thousands**               | 3 Months Ended | 9 Months Ended |
|------------------------------------------------------------------------------------------------------|----------------|----------------|
||
| **Accumulated Other Comprehensive Income (Loss) [Line Items]**                                       |           |           |   |   |
| TOTAL OTHER COMPREHENSIVE (LOSS)/INCOME, NET OF TAX                                                  | $ (17,039)     | $ 56,966       | $ 115,995 | $ 27,681 |
| **AOCI Attributable to Parent, Net of Tax [Roll Forward]**                                           |           |           |   |   |
| Beginning Balance                                                                                    |           |           | 19,402,130 |   |
| Net Activity                                                                                         | (17,039)       | 56,966         | 115,995 | 27,681 |
| Ending Balance                                                                                       | 19,756,345     |           | 19,756,345 |   |
| Net unrealized gains/(losses) on cash flow hedge derivative financial instruments                    |           |           |   |   |
| **Accumulated Other Comprehensive Income (Loss) [Line Items]**                                       |           |           |   |   |
| Other comprehensive income/(loss), pretax activity                                                   | 69,464         | (45,805)       | (11,538) | (67,051) |
| Other comprehensive income/(loss), tax effect                                                        | (15,775)       | 16,975         | 15,117 | 25,226 |
| Other comprehensive income/(loss), net activity                                                      | 53,689         | (28,830)       | 3,579 | (41,825) |
| Reclassification adjustment, pretax activity                                                         | 254            | 1,774          | 4,379 | 9,957 |
| Reclassification adjustment, tax effect                                                              | (115)          | (657)          | (1,430) | (3,746) |
| Reclassification adjustment, net activity                                                            | 139            | 1,117          | 2,949 | 6,211 |
| Total other comprehensive income/(loss), pretax activity                                             | 69,718         | (44,031)       | (7,159) | (57,094) |
| Total other comprehensive income/(loss), tax effect                                                  | (15,890)       | 16,318         | 13,687 | 21,480 |
| TOTAL OTHER COMPREHENSIVE (LOSS)/INCOME, NET OF TAX                                                  | 53,828         | (27,713)       | 6,528 | (35,614) |
| **AOCI Attributable to Parent, Net of Tax [Roll Forward]**                                           |           |           |   |   |
| Beginning Balance                                                                                    | (63,881)       | (22,161)       | (16,581) | (14,260) |
| Net Activity                                                                                         | 53,828         | (27,713)       | 6,528 | (35,614) |
| Ending Balance                                                                                       | (10,053)       | (49,874)       | (10,053) | (49,874) |
| Net unrealized (losses)/gains on investment securities available-for-sale                            |           |           |   |   |
| **Accumulated Other Comprehensive Income (Loss) [Line Items]**                                       |           |           |   |   |
| Other comprehensive income/(loss), pretax activity                                                   | (105,270)      | 135,553        | 246,508 | 119,696 |
| Other comprehensive income/(loss), tax effect                                                        | 38,852         | (52,711)       | (99,376) | (47,692) |
| Other comprehensive income/(loss), net activity                                                      | (66,418)       | 82,842         | 147,132 | 72,004 |
| Reclassification adjustment, pretax activity                                                         |           |           | (57,726) | (17,271) |
| Reclassification adjustment, tax effect                                                              |           |           | 23,380 | 6,890 |
| Reclassification adjustment, net activity                                                            |           |           | (34,346) | (10,381) |
| Total other comprehensive income/(loss), pretax activity                                             | (105,270)      | 137,546        | 188,782 | 102,425 |
| Total other comprehensive income/(loss), tax effect                                                  | 38,852         | (53,488)       | (75,996) | (40,802) |
| TOTAL OTHER COMPREHENSIVE (LOSS)/INCOME, NET OF TAX                                                  | (66,418)       | 84,058         | 112,786 | 61,623 |
| **AOCI Attributable to Parent, Net of Tax [Roll Forward]**                                           |           |           |   |   |
| Beginning Balance                                                                                    | 83,262         | (74,275)       | (95,942) | (51,840) |
| Net Activity                                                                                         | (66,418)       | 84,058         | 112,786 | 61,623 |
| Ending Balance                                                                                       | 16,844         | 9,783          | 16,844 | 9,783 |
| Reclassification adjustment for net loss included in net income/(expense) on non-OTTI securities (2) |           |           |   |   |
| **Accumulated Other Comprehensive Income (Loss) [Line Items]**                                       |           |           |   |   |
| Reclassification adjustment, pretax activity                                                         |           | 1,993          | (57,770) | (18,363) |
| Reclassification adjustment, tax effect                                                              |           | (777)          | 23,398 | 7,325 |
| Reclassification adjustment, net activity                                                            |           | 1,216          | (34,372) | (11,038) |
| Reclassification adjustment for net losses/(gains) included in net income on OTTI securities         |           |           |   |   |
| **Accumulated Other Comprehensive Income (Loss) [Line Items]**                                       |           |           |   |   |
| Reclassification adjustment, pretax activity                                                         |           |           | 44 | 1,092 |
| Reclassification adjustment, tax effect                                                              |           |           | (18) | (435) |
| Reclassification adjustment, net activity                                                            |           |           | 26 | 657 |
| Pension and post-retirement actuarial gain/(loss)                                                    |           |           |   |   |
| **Accumulated Other Comprehensive Income (Loss) [Line Items]**                                       |           |           |   |   |
| Total other comprehensive income/(loss), pretax activity                                             | (4,085)        | 1,019          | (2,227) | 3,054 |
| Total other comprehensive income/(loss), tax effect                                                  | (364)          | (398)          | (1,092) | (1,382) |
| TOTAL OTHER COMPREHENSIVE (LOSS)/INCOME, NET OF TAX                                                  | (4,449)        | 621            | (3,319) | 1,672 |
| **AOCI Attributable to Parent, Net of Tax [Roll Forward]**                                           |           |           |   |   |
| Beginning Balance                                                                                    | (56,877)       | (61,116)       | (58,007) | (62,167) |
| Net Activity                                                                                         | (4,449)        | 621            | (3,319) | 1,672 |
| Ending Balance                                                                                       | (61,326)       | (60,495)       | (61,326) | (60,495) |
| Accumulated Other Comprehensive (Loss)/Income                                                        |           |           |   |   |
| **Accumulated Other Comprehensive Income (Loss) [Line Items]**                                       |           |           |   |   |
| Total other comprehensive income/(loss), pretax activity                                             | (39,637)       | 94,534         | 179,396 | 48,385 |
| Total other comprehensive income/(loss), tax effect                                                  | 22,598         | (37,568)       | (63,401) | (20,704) |
| TOTAL OTHER COMPREHENSIVE (LOSS)/INCOME, NET OF TAX                                                  | (17,039)       | 56,966         | 115,995 | 27,681 |
| **AOCI Attributable to Parent, Net of Tax [Roll Forward]**                                           |           |           |   |   |
| Beginning Balance                                                                                    | (37,496)       | (157,552)      | (170,530) | (128,267) |
| Net Activity                                                                                         | (17,039)       | 56,966         | 115,995 | 27,681 |
| Ending Balance                                                                                       | $ (54,535)     | $ (100,586)    | $ (54,535) | $ (100,586) |

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.
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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.
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Amount before tax and reclassification adjustments of other comprehensive income (loss).
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Amount after tax, before reclassification adjustments of other comprehensive income (loss).
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Amount before tax, after reclassification adjustments of other comprehensive income (loss).
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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.
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