| **LOANS AND ALLOWANCE FOR CREDIT LOSSES (Narrative) (Details) $ in Thousands**                                                                                                                                                                                                                                                                                                                              | 6 Months Ended | 12 Months Ended |              |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------|-----------------|--------------|
||
| **Loans Receivable [Line Items]**                                                                                                                                                                                                                                                                                                                                                                           |                |            |         |   |
| Threshold period past due for nonaccrual status                                                                                                                                                                                                                                                                                                                                                             |                | 60 days         |         |   |
| Percentage of payments made to classify as current                                                                                                                                                                                                                                                                                                                                                          |                | 50.00%          |         |   |
| Threshold period past due for account to be contractually delinquent                                                                                                                                                                                                                                                                                                                                        |                | 120 days        |         |   |
| Loans pledged as collateral                                                                                                                                                                                                                                                                                                                                                                                 |                | $ 54,300,000    | $ 59,300,000 |   |
| Loans held-for-sale                                                                                                                                                                                                                                                                                                                                                                                         | [1]            | 3,257,158       | 3,183,282    |   |
| Accrued interest receivable                                                                                                                                                                                                                                                                                                                                                                                 | [2]            | 552,021         | 586,263      |   |
| Troubled debt restructurings                                                                                                                                                                                                                                                                                                                                                                                |                | $ 5,135,965     | 4,399,546    |   |
| TDR, threshold period of sustained repayment performance                                                                                                                                                                                                                                                                                                                                                    |                | 6 months        |         |   |
| TDRs, number of days past due after modification considered to have subsequently defaulted                                                                                                                                                                                                                                                                                                                  |                | 90 days         |         |   |
| TDR, threshold period loan needed to remain current prior to modification to remain on accrual status                                                                                                                                                                                                                                                                                                       |                | 6 months        |         |   |
| Performing                                                                                                                                                                                                                                                                                                                                                                                                  |                |            |         |   |
| **Loans Receivable [Line Items]**                                                                                                                                                                                                                                                                                                                                                                           |                |            |         |   |
| Interest income                                                                                                                                                                                                                                                                                                                                                                                             |                | $ 338,800       | 439,600      |   |
| Troubled debt restructurings                                                                                                                                                                                                                                                                                                                                                                                |                | 4,429,024       | 3,797,231    |   |
| Loans receivable                                                                                                                                                                                                                                                                                                                                                                                            |                |            |         |   |
| **Loans Receivable [Line Items]**                                                                                                                                                                                                                                                                                                                                                                           |                |            |         |   |
| Accrued interest receivable                                                                                                                                                                                                                                                                                                                                                                                 |                | $ 511,800       | 521,100      |   |
| Retail Installment Contracts                                                                                                                                                                                                                                                                                                                                                                                |                |            |         |   |
| **Loans Receivable [Line Items]**                                                                                                                                                                                                                                                                                                                                                                           |                |            |         |   |
| Threshold period past due for nonaccrual status                                                                                                                                                                                                                                                                                                                                                             |                | 60 days         |         |   |
| Personal unsecured loans | Consumer                                                                                                                                                                                                                                                                                                                                                                         |                |            |         |   |
| **Loans Receivable [Line Items]**                                                                                                                                                                                                                                                                                                                                                                           |                |            |         |   |
| Loans held-for-sale                                                                                                                                                                                                                                                                                                                                                                                         |                | $ 970,700       | $ 2,000,000  |   |
| Retail installment contracts                                                                                                                                                                                                                                                                                                                                                                                |                |            |         |   |
| **Loans Receivable [Line Items]**                                                                                                                                                                                                                                                                                                                                                                           |                |            |         |   |
| TDRs, number of days past due after modification considered to have subsequently defaulted                                                                                                                                                                                                                                                                                                                  |                | 120 days        |         |   |
| Commercial real estate loans | Commercial                                                                                                                                                                                                                                                                                                                                                                   |                |            |         |   |
| **Loans Receivable [Line Items]**                                                                                                                                                                                                                                                                                                                                                                           |                |            |         |   |
| Number of business lines | business_line                                                                                                                                                                                                                                                                                                                                                                    |                | 3               |         |   |
| SC | Personal unsecured loans | Consumer                                                                                                                                                                                                                                                                                                                                                                    |                |            |         |   |
| **Loans Receivable [Line Items]**                                                                                                                                                                                                                                                                                                                                                                           |                |            |         |   |
| Loans receivable held-for-sale                                                                                                                                                                                                                                                                                                                                                                              |                |            |         | $ 869,300 |
| FCA                                                                                                                                                                                                                                                                                                                                                                                                         |                |            |         |   |
| **Loans Receivable [Line Items]**                                                                                                                                                                                                                                                                                                                                                                           |                |            |         |   |
| Percentage of payments made to classify as current                                                                                                                                                                                                                                                                                                                                                          |                | 90.00%          |         |   |
|                                                                                                                                                                                                                                                                                                                                                                                                             |
| [1]Recorded at the fair value option ("FVO") or lower of cost or fair value.[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. |

| X                                                                                                                                                                                                                                                                                                                                                                           |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
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Financing Receivable, Percentage of Payment to Classify as Current
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| - Definition
Financing Receivables, Modifications, Threshold Period of Sustained Repayment Performance
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| X                                                                                                                                                                                                                              |
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| - Definition
Number of Business Lines
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| - Definition
Troubled Debt Restructuring, Number of Days Past Due After Modification Considered Subsequently Defaulted
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| - Definition
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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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.
+ References
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.
+ References
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The gross interest income that would have been recorded in the period on troubled debt restructurings, if the loans had been current in accordance with their original terms and had been outstanding throughout the period or since origination, if held for part of the period.
+ References
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| X                                                                                                                                                                                                                                                                                                                                               |
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| - Definition
Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Carrying amount as of the balance sheet date of loans that have been pledged as collateral for borrowings. If the secured party has the right by contract or custom to sell or re-pledge the collateral, then the debtor reclassifies that asset and report that asset in its statement of financial position separately from other assets not so encumbered.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The face amount of loans that will be sold to other entities.
+ References
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount, after allowance for bad debt, of loan receivables held-for-sale that are not part of a disposal group. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.
+ References
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| - Definition
Threshold period past due for financing receivable to write off as uncollectible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
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