| **BUSINESS SEGMENT INFORMATION (Details) - USD ($)**     |          | 3 Months Ended  | 9 Months Ended  |
|----------------------------------------------------------|----------|-----------------|-----------------|
||
| **Segment Reporting Information [Line Items]**           |     |            |            |   |   |
| Net interest income                                      |     | $ 1,683,262,000 | $ 1,625,476,000 | $ 5,099,515,000 | $ 4,387,615,000 |
| Total non-interest income                                |     | 835,961,000     | 643,826,000     | 2,304,558,000 | 1,714,833,000 |
| Gain on change in control                                |     | 0               | 0               | 0 | 2,428,539,000 |
| Provision for credit losses                              |     | 854,180,000     | 1,013,357,000   | 2,728,118,000 | 2,034,721,000 |
| Total expenses                                           |     | 1,241,155,000   | 960,751,000     | 3,498,106,000 | 2,734,361,000 |
| Income/(loss) before income taxes                        |     | 423,888,000     | 295,194,000     | 1,177,849,000 | 3,761,905,000 |
| Intersegment (expense)/revenue                           |     | 0               | 0               | 0 | 0 |
| Total average assets                                     |     | 128,995,997,000 | 112,609,244,000 | 123,803,672,000 | 106,192,458,000 |
| Global Corporate Banking                                 |     |            |            |   |   |
| **Segment Reporting Information [Line Items]**           |     |            |            |   |   |
| Minimum annual revenue to service corporations           |     | 500,000,000     |            | 500,000,000 |   |
| Operating Segments | Retail Banking                      |     |            |            |   |   |
| **Segment Reporting Information [Line Items]**           |     |            |            |   |   |
| Net interest income                                      |     | 175,417,000     | 166,555,000     | 512,584,000 | 497,851,000 |
| Total non-interest income                                |     | 60,206,000      | 128,774,000     | 213,064,000 | 280,088,000 |
| Provision for credit losses                              |     | 18,800,000      | 35,251,000      | 47,033,000 | 51,308,000 |
| Total expenses                                           |     | 284,969,000     | 259,799,000     | 839,119,000 | 767,240,000 |
| Income/(loss) before income taxes                        |     | (68,146,000)    | 279,000         | (160,504,000) | (40,609,000) |
| Intersegment (expense)/revenue                           |     | 66,568,000      | 27,342,000      | 183,780,000 | 77,836,000 |
| Total average assets                                     |     | 16,871,108,000  | 17,833,597,000  | 17,065,573,000 | 17,866,900,000 |
| Operating Segments | Auto Finance & Business Banking |     |            |            |   |   |
| **Segment Reporting Information [Line Items]**           |     |            |            |   |   |
| Net interest income                                      |     | 63,418,000      | 61,293,000      | 187,654,000 | 180,088,000 |
| Total non-interest income                                |     | 104,947,000     | 76,012,000      | 306,320,000 | 142,515,000 |
| Provision for credit losses                              |     | 7,017,000       | 2,868,000       | 18,452,000 | 4,779,000 |
| Total expenses                                           |     | 102,781,000     | 75,821,000      | 302,750,000 | 146,519,000 |
| Income/(loss) before income taxes                        |     | 58,567,000      | 58,616,000      | 172,772,000 | 171,305,000 |
| Intersegment (expense)/revenue                           |     | 5,136,000       | 5,649,000       | 12,175,000 | 15,902,000 |
| Total average assets                                     |     | 8,440,985,000   | 7,027,225,000   | 8,374,508,000 | 6,217,471,000 |
| Operating Segments | Real Estate and Commercial Banking  |     |            |            |   |   |
| **Segment Reporting Information [Line Items]**           |     |            |            |   |   |
| Net interest income                                      |     | 115,514,000     | 107,924,000     | 338,678,000 | 310,761,000 |
| Total non-interest income                                |     | 34,930,000      | 17,986,000      | 72,610,000 | 61,514,000 |
| Provision for credit losses                              |     | 3,897,000       | (59,849,000)    | 22,868,000 | (63,135,000) |
| Total expenses                                           |     | 43,168,000      | 39,386,000      | 129,945,000 | 110,335,000 |
| Income/(loss) before income taxes                        |     | 103,379,000     | 146,373,000     | 258,475,000 | 325,075,000 |
| Intersegment (expense)/revenue                           |     | (65,233,000)    | (79,516,000)    | (200,550,000) | (242,454,000) |
| Total average assets                                     |     | 21,849,120,000  | 20,511,518,000  | 21,138,122,000 | 20,355,225,000 |
| Operating Segments | Global Corporate Banking            |     |            |            |   |   |
| **Segment Reporting Information [Line Items]**           |     |            |            |   |   |
| Net interest income                                      |     | 54,475,000      | 46,586,000      | 157,806,000 | 131,780,000 |
| Total non-interest income                                |     | 17,280,000      | 19,700,000      | 60,961,000 | 57,513,000 |
| Provision for credit losses                              |     | 4,570,000       | 7,990,000       | 9,514,000 | 6,228,000 |
| Total expenses                                           |     | 18,981,000      | 18,160,000      | 63,483,000 | 55,391,000 |
| Income/(loss) before income taxes                        |     | 48,204,000      | 40,136,000      | 145,770,000 | 127,674,000 |
| Intersegment (expense)/revenue                           |     | (10,199,000)    | (10,162,000)    | (30,039,000) | (30,077,000) |
| Total average assets                                     |     | 12,093,666,000  | 9,812,825,000   | 11,573,651,000 | 9,161,992,000 |
| Operating Segments | SCUSA                               |     |            |            |   |   |
| **Segment Reporting Information [Line Items]**           |     |            |            |   |   |
| Net interest income                                      |     | 1,231,539,000   | 1,092,698,000   | 3,620,089,000 | 3,238,551,000 |
| Total non-interest income                                |     | 478,873,000     | 374,872,000     | 1,435,354,000 | 927,958,000 |
| Provision for credit losses                              |     | 744,143,000     | 770,105,000     | 2,088,857,000 | 2,057,260,000 |
| Total expenses                                           |     | 613,263,000     | 415,403,000     | 1,736,210,000 | 1,307,851,000 |
| Income/(loss) before income taxes                        |     | 353,006,000     | 282,062,000     | 1,230,376,000 | 801,398,000 |
| Intersegment (expense)/revenue                           |     | 0               | 0               | 0 | 0 |
| Total average assets                                     |     | 35,478,456,000  | 30,648,333,000  | 34,352,761,000 | 26,160,378,000 |
| Corporate, Non-Segment | Other                           |     |            |            |   |   |
| **Segment Reporting Information [Line Items]**           |     |            |            |   |   |
| Net interest income                                      |     | (23,080,000)    | 19,696,000      | (25,245,000) | 62,039,000 |
| Total non-interest income                                |     | 24,779,000      | 39,495,000      | 67,295,000 | 96,987,000 |
| Provision for credit losses                              |     | (52,908,000)    | 13,740,000      | (32,490,000) | (39,181,000) |
| Total expenses                                           |     | 174,343,000     | 194,770,000     | 442,311,000 | 537,435,000 |
| Income/(loss) before income taxes                        |     | (119,736,000)   | (149,319,000)   | (367,771,000) | (339,228,000) |
| Intersegment (expense)/revenue                           |     | 3,728,000       | 56,687,000      | 34,634,000 | 178,793,000 |
| Total average assets                                     |     | 34,262,662,000  | 26,775,746,000  | 31,299,057,000 | 26,430,492,000 |
| Purchase Price Adjustments | SCUSA                       |     |            |            |   |   |
| **Segment Reporting Information [Line Items]**           |     |            |            |   |   |
| Net interest income                                      |     | 65,863,000      | 130,695,000     | 307,689,000 | 310,652,000 |
| Total non-interest income                                |     | 119,409,000     | (4,075,000)     | 170,391,000 | 241,067,000 |
| Gain on change in control                                |     |            |            |   | 2,428,539,000 |
| Provision for credit losses                              |     | 128,661,000     | 243,252,000     | 573,884,000 | 242,915,000 |
| Total expenses                                           |     | 12,099,000      | (35,086,000)    | 8,270,000 | 70,066,000 |
| Income/(loss) before income taxes                        |     | 44,512,000      | (81,546,000)    | (104,074,000) | 2,667,277,000 |
| Intersegment (expense)/revenue                           |     | 0               | 0               | 0 | 0 |
| Total average assets                                     |     | 0               | 0               | 0 | 0 |
| Eliminations                                             |     |            |            |   |   |
| **Segment Reporting Information [Line Items]**           |     |            |            |   |   |
| Net interest income                                      |     | 116,000         | 29,000          | 260,000 | (344,107,000) |
| Total non-interest income                                |     | (4,463,000)     | (8,938,000)     | (21,437,000) | (92,809,000) |
| Provision for credit losses                              |     | 0               | 0               | 0 | (225,453,000) |
| Total expenses                                           |     | (8,449,000)     | (7,502,000)     | (23,982,000) | (260,476,000) |
| Income/(loss) before income taxes                        |     | 4,102,000       | (1,407,000)     | 2,805,000 | 49,013,000 |
| Intersegment (expense)/revenue                           |     | 0               | 0               | 0 | 0 |
| Total average assets                                     |     | $ 0             | $ 0             | $ 0 | $ 0 |
| Chrysler Group                                           |     |            |            |   |   |
| **Segment Reporting Information [Line Items]**           |     |            |            |   |   |
| Private label financing agreement, term                  | 10 years |            |            |   |   |

| X                                                                                                                                                                                                                                                                                                                                                        |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fees and Other Income Including Realized Gains (Losses) on Sale of Investment Securities
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No definition available.
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| - Definition
Gain on Change in Control
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| - Definition
General and administrative and other expenses
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No definition available.
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| - Definition
Minimum Annual Revenue to Service Corporation
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No definition available.
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| X                                                                                                                                                                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of average assets attributed to the reportable segment.
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| - Definition
Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
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No definition available.
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.
+ References
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The net amount of operating interest income (expense).
+ References
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.
+ References
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).
+ References
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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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No definition available.
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