| **BASIS OF PRESENTATION AND ACCOUNTING POLICIES (Correction of Error, Impact on Loans) (Details) - USD ($) $ in Thousands**                                        | Mar. 31, 2019 | Dec. 31, 2018 | Mar. 31, 2018 |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|---------------|
| **Error Corrections and Prior Period Adjustments Restatement [Line Items]**                                                                                        |          |          |          |
| Total Past Due                                                                                                                                                     | $ 4,766,469   | $ 5,714,660   |          |
| Current                                                                                                                                                            | 85,650,369    | 82,614,486    | $ 77,704,486  |
| As Reported                                                                                                                                                        |          |          |          |
| **Error Corrections and Prior Period Adjustments Restatement [Line Items]**                                                                                        |          |          |          |
| Current                                                                                                                                                            |          |          | 77,771,558    |
| Corrections | Correction of Errors in Accounting for Retail Installment Contracts and Auto Loans                                                                   |          |          |          |
| **Error Corrections and Prior Period Adjustments Restatement [Line Items]**                                                                                        |          |          |          |
| Current                                                                                                                                                            |          |          | (67,072)      |
| 30-89 DPD                                                                                                                                                          |          |          |          |
| **Error Corrections and Prior Period Adjustments Restatement [Line Items]**                                                                                        |          |          |          |
| Total Past Due                                                                                                                                                     | 3,989,462     | 4,772,117     | 3,652,230     |
| 30-89 DPD | As Reported                                                                                                                                            |          |          |          |
| **Error Corrections and Prior Period Adjustments Restatement [Line Items]**                                                                                        |          |          |          |
| Total Past Due                                                                                                                                                     |          |          | 3,509,299     |
| 30-89 DPD | Corrections | Correction of Errors in Accounting for Retail Installment Contracts and Auto Loans                                                       |          |          |          |
| **Error Corrections and Prior Period Adjustments Restatement [Line Items]**                                                                                        |          |          |          |
| Total Past Due                                                                                                                                                     |          |          | 142,931       |
| 90 or Greater DPD                                                                                                                                                  |          |          |          |
| **Error Corrections and Prior Period Adjustments Restatement [Line Items]**                                                                                        |          |          |          |
| Total Past Due                                                                                                                                                     | 777,007       | 942,543       | 817,762       |
| 90 or Greater DPD | As Reported                                                                                                                                    |          |          |          |
| **Error Corrections and Prior Period Adjustments Restatement [Line Items]**                                                                                        |          |          |          |
| Total Past Due                                                                                                                                                     |          |          | 798,166       |
| 90 or Greater DPD | Corrections | Correction of Errors in Accounting for Retail Installment Contracts and Auto Loans                                               |          |          |          |
| **Error Corrections and Prior Period Adjustments Restatement [Line Items]**                                                                                        |          |          |          |
| Total Past Due                                                                                                                                                     |          |          | 19,596        |
| Consumer | RICs and auto loans - originated                                                                                                                        |          |          |          |
| **Error Corrections and Prior Period Adjustments Restatement [Line Items]**                                                                                        |          |          |          |
| Total Past Due                                                                                                                                                     | 3,546,773     | 4,495,834     |          |
| Current                                                                                                                                                            | 26,296,475    | 24,036,251    | 21,273,648    |
| Consumer | RICs and auto loans - originated | As Reported                                                                                                          |          |          |          |
| **Error Corrections and Prior Period Adjustments Restatement [Line Items]**                                                                                        |          |          |          |
| Current                                                                                                                                                            |          |          | 21,340,720    |
| Consumer | RICs and auto loans - originated | Corrections | Correction of Errors in Accounting for Retail Installment Contracts and Auto Loans                     |          |          |          |
| **Error Corrections and Prior Period Adjustments Restatement [Line Items]**                                                                                        |          |          |          |
| Current                                                                                                                                                            |          |          | (67,072)      |
| Consumer | 30-89 DPD | RICs and auto loans - originated                                                                                                            |          |          |          |
| **Error Corrections and Prior Period Adjustments Restatement [Line Items]**                                                                                        |          |          |          |
| Total Past Due                                                                                                                                                     | 3,247,752     | 4,076,015     | 2,777,295     |
| Consumer | 30-89 DPD | RICs and auto loans - originated | As Reported                                                                                              |          |          |          |
| **Error Corrections and Prior Period Adjustments Restatement [Line Items]**                                                                                        |          |          |          |
| Total Past Due                                                                                                                                                     |          |          | 2,634,364     |
| Consumer | 30-89 DPD | RICs and auto loans - originated | Corrections | Correction of Errors in Accounting for Retail Installment Contracts and Auto Loans         |          |          |          |
| **Error Corrections and Prior Period Adjustments Restatement [Line Items]**                                                                                        |          |          |          |
| Total Past Due                                                                                                                                                     |          |          | 142,931       |
| Consumer | 90 or Greater DPD | RICs and auto loans - originated                                                                                                    |          |          |          |
| **Error Corrections and Prior Period Adjustments Restatement [Line Items]**                                                                                        |          |          |          |
| Total Past Due                                                                                                                                                     | $ 299,021     | $ 419,819     | 248,407       |
| Consumer | 90 or Greater DPD | RICs and auto loans - originated | As Reported                                                                                      |          |          |          |
| **Error Corrections and Prior Period Adjustments Restatement [Line Items]**                                                                                        |          |          |          |
| Total Past Due                                                                                                                                                     |          |          | 228,811       |
| Consumer | 90 or Greater DPD | RICs and auto loans - originated | Corrections | Correction of Errors in Accounting for Retail Installment Contracts and Auto Loans |          |          |          |
| **Error Corrections and Prior Period Adjustments Restatement [Line Items]**                                                                                        |          |          |          |
| Total Past Due                                                                                                                                                     |          |          | $ 19,596      |

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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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Financing receivables that are current.
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Recorded Investment in financing receivables that are past due at the balance sheet date.
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