| **FAIR VALUE (Reconciliation of Assets and Liabilities Using Level 3 Inputs) (Details) - Level 3 - Recurring - USD ($) $ in Thousands** | 3 Months Ended | 9 Months Ended |
|-----------------------------------------------------------------------------------------------------------------------------------------|----------------|----------------|
||
| **Fair Value, Assets, Unobservable Input Reconciliation [Roll Forward]**                                                                |           |           |   |   |
| Balance at beginning of period                                                                                                          | $ 2,192,754    | $ 2,644,803    | $ 2,261,316 | $ 194,891 |
| Gains (Losses) in other comprehensive income                                                                                            | (5,307)        | (849)          | (8,961) | 1,021 |
| Gains/(losses) in earnings                                                                                                              | 29,328         | 111,333        | 222,653 | 462,741 |
| Additions/Issuances                                                                                                                     | 317,335        | 85,621         | 927,259 | 2,062,333 |
| Settlements                                                                                                                             | (388,613)      | (506,416)      | (1,256,770) | (1,557,954) |
| Transfers into level 3                                                                                                                  |           |           |   | 1,171,460 |
| Balance at end of period                                                                                                                | 2,145,497      | 2,334,492      | 2,145,497 | 2,334,492 |
| Changes in unrealized gains (losses) included in earnings related to balances still held at end of period                               | 25,733         | 113,360        | 220,236 | 461,223 |
| Investments Available-for-Sale                                                                                                          |           |           |   |   |
| **Fair Value, Assets, Unobservable Input Reconciliation [Roll Forward]**                                                                |           |           |   |   |
| Balance at beginning of period                                                                                                          | 1,539,483      | 1,243,872      | 1,267,643 | 52,940 |
| Gains (Losses) in other comprehensive income                                                                                            | (5,307)        | (849)          | (8,961) | 1,021 |
| Gains/(losses) in earnings                                                                                                              | 0              | 0              | 0 | 0 |
| Additions/Issuances                                                                                                                     | 311,540        | 69,543         | 910,135 | 171,869 |
| Settlements                                                                                                                             | (222,989)      | (138,107)      | (546,090) | (222,831) |
| Transfers into level 3                                                                                                                  |           |           |   | 1,171,460 |
| Balance at end of period                                                                                                                | 1,622,727      | 1,174,459      | 1,622,727 | 1,174,459 |
| Changes in unrealized gains (losses) included in earnings related to balances still held at end of period                               | 0              | 0              | 0 | 0 |
| Retail Installment Contracts Held for Investment                                                                                        |           |           |   |   |
| **Fair Value, Assets, Unobservable Input Reconciliation [Roll Forward]**                                                                |           |           |   |   |
| Balance at beginning of period                                                                                                          | 494,651        | 1,273,072      | 845,911 | 0 |
| Gains (Losses) in other comprehensive income                                                                                            | 0              | 0              | 0 | 0 |
| Gains/(losses) in earnings                                                                                                              | 39,296         | 116,177        | 219,837 | 475,607 |
| Additions/Issuances                                                                                                                     | 0              | 0              | 0 | 1,870,383 |
| Settlements                                                                                                                             | (159,789)      | (362,737)      | (691,590) | (1,319,478) |
| Transfers into level 3                                                                                                                  |           |           |   | 0 |
| Balance at end of period                                                                                                                | 374,158        | 1,026,512      | 374,158 | 1,026,512 |
| Changes in unrealized gains (losses) included in earnings related to balances still held at end of period                               | 39,296         | 116,177        | 219,837 | 475,607 |
| MSRs                                                                                                                                    |           |           |   |   |
| **Fair Value, Assets, Unobservable Input Reconciliation [Roll Forward]**                                                                |           |           |   |   |
| Balance at beginning of period                                                                                                          | 157,147        | 124,118        | 145,047 | 141,787 |
| Gains (Losses) in other comprehensive income                                                                                            | 0              | 0              | 0 | 0 |
| Gains/(losses) in earnings                                                                                                              | (13,472)       | (2,726)        | 749 | (14,078) |
| Additions/Issuances                                                                                                                     | 5,795          | 16,078         | 17,124 | 20,081 |
| Settlements                                                                                                                             | (5,935)        | (5,679)        | (19,385) | (15,999) |
| Transfers into level 3                                                                                                                  |           |           |   | 0 |
| Balance at end of period                                                                                                                | 143,535        | 131,791        | 143,535 | 131,791 |
| Changes in unrealized gains (losses) included in earnings related to balances still held at end of period                               | (13,472)       | (2,726)        | 749 | (14,078) |
| Derivatives                                                                                                                             |           |           |   |   |
| **Fair Value, Assets, Unobservable Input Reconciliation [Roll Forward]**                                                                |           |           |   |   |
| Balance at beginning of period                                                                                                          | 1,473          | 3,741          | 2,715 | 164 |
| Gains (Losses) in other comprehensive income                                                                                            | 0              | 0              | 0 | 0 |
| Gains/(losses) in earnings                                                                                                              | 3,504          | (2,118)        | 2,067 | 1,212 |
| Additions/Issuances                                                                                                                     | 0              | 0              | 0 | 0 |
| Settlements                                                                                                                             | 100            | 107            | 295 | 354 |
| Transfers into level 3                                                                                                                  |           |           |   | 0 |
| Balance at end of period                                                                                                                | 5,077          | 1,730          | 5,077 | 1,730 |
| Changes in unrealized gains (losses) included in earnings related to balances still held at end of period                               | $ (91)         | $ (91)         | $ (350) | $ (306) |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of unrealized (holding) gain (loss) which is included in the statement of income (or changes in net assets) related to those assets still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3).
+ References
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| - Definition
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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No definition available.
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| - Definition
Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
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| - Definition
Amount of gain (loss) recognized in other comprehensive income (loss) for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.
+ References
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| - Definition
Amount of issuances of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.
+ References
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| - Definition
Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
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| - Definition
Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.
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| - Definition
Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.
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