| **LOANS AND ALLOWANCE FOR CREDIT LOSSES (Retail Installment Contracts and Auto Loans) (Details) - USD ($) $ in Thousands**                                                                                                                                                                                                                                                                                                                                                                                      | Jun. 30, 2016 | Dec. 31, 2015 |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Loans Receivable [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |               |          |   |
| Total loans held for investment                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 | [1],[2]       | $ 80,570,776  | $ 79,373,792 |
| Consumer                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |          |   |
| **Loans Receivable [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |               |          |   |
| Total loans held for investment                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |               | 39,470,460    | 38,748,072 |
| Consumer | Retail installment contracts and auto loans - originated                                                                                                                                                                                                                                                                                                                                                                                                                                             |               |          |   |
| **Loans Receivable [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |               |          |   |
| Total loans held for investment                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |               | 25,533,755    | 24,647,798 |
| Consumer | Retail installment contracts, purchased                                                                                                                                                                                                                                                                                                                                                                                                                                                              |               |          |   |
| **Loans Receivable [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |               |          |   |
| UPB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |               | 5,063,379     | 6,709,748 |
| UPB - FVO                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |               | 72,082        | 140,995 |
| Total UPB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |               | 5,135,461     | 6,850,743 |
| Purchase Marks                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |               | (505,646)     | (742,533) |
| Total loans held for investment                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |               | 4,629,815     | 6,108,210 |
| Purchase Marks, FVO                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |               | 16,500        | 33,100 |
| Consumer | Retail installment contracts, originated                                                                                                                                                                                                                                                                                                                                                                                                                                                             |               |          |   |
| **Loans Receivable [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |               |          |   |
| Total UPB                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |               | 21,439,684    | 19,069,801 |
| Total loans held for investment                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |               | 20,886,690    | 18,521,744 |
| Net Discounts                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |               | (552,994)     | (548,057) |
| Consumer | Auto loan                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |               |          |   |
| **Loans Receivable [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |               |          |   |
| Total loans held for investment                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |               | 17,250        | 17,844 |
| Consumer | Retail installment contracts, originated, post-change in control                                                                                                                                                                                                                                                                                                                                                                                                                                     |               |          |   |
| **Loans Receivable [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |               |          |   |
| Total loans held for investment                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |               | $ 20,903,940  | $ 18,539,588 |
|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| [1]Loans held-for-investment ("LHFI") includes $250.7 million and $328.7 million of loans recorded at fair value at June 30, 2016 and December 31, 2015, respectively.[2]The Company has interests in certain securitization trusts ("Trusts") that are considered variable interest entities ("VIEs") for accounting purposes. The Company consolidates VIEs where it is deemed the primary beneficiary. See Note 6 to these Condensed Consolidated Financial Statements for additional information. |

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.
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