| **GOODWILL AND OTHER INTANGIBLES (Tables)**                             | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
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| **Goodwill and Intangible Assets Disclosure [Abstract]**                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| Schedule of Goodwill                                                    | The following table presents activity in the Company's goodwill by its reporting units for the quarter ended March 31, 2015:  Retail Banking Auto Finance & Alliances Real Estate and Commercial Banking Global Banking & Markets and Large Corporate SCUSA Total  (in thousands)Goodwill at December 31, 2014 $1,815,729 $71,522 $1,406,048 $131,130 $5,467,582 $8,892,011Additions / disposals during the period — — — — — —Goodwill at March 31, 2015 $1,815,729 $71,522 $1,406,048 $131,130 $5,467,582 $8,892,011                                                                                                                                                                                                                                                                                                                                              |
| Schedule of Finite-Lived and Indefinite-Lived Intangible Assets         | The following table details amounts related to the Company's finite-lived and indefinite-lived intangible assets for the dates indicated. NOTE 8. GOODWILL AND OTHER INTANGIBLES (continued) March 31, 2015 December 31, 2014 NetCarryingAmount AccumulatedAmortization NetCarryingAmount AccumulatedAmortization (in thousands)Intangibles subject to amortization:       Dealer networks$534,250 $(45,750) $544,054 $(35,946)Chrysler Relationship121,250 (17,500) 125,000 (13,750)Core deposit intangibles5,338 (290,504) 7,779 (288,063)Other intangibles7,843 (22,065) 8,655 (21,253)Total intangibles subject to amortization668,681 (375,819) 685,488 (359,012)Intangibles not subject to amortization:       Trade name50,000 — 50,000 —Total Intangibles$718,681 $(375,819) $735,488 $(359,012) |
| Schedule of Finite-Lived Intangible Assets, Future Amortization Expense | The estimated aggregate amortization expense related to intangibles for each of the five succeeding calendar years ending December 31 is:Year Calendar Year Amount Recorded To Date Remaining Amount To Record  (in thousands)2015 $64,432 $16,806 $47,6262016 57,163 — 57,1632017 55,055 — 55,0552018 54,702 — 54,7022019 54,501 — 54,501Thereafter 399,634 — 399,634                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |

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| - Definition
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Table Text Block]
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No definition available.
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| - Definition
Tabular disclosure of the amount of amortization expense expected to be recorded in succeeding fiscal years for finite-lived intangible assets.
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Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275
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| - Definition
Tabular disclosure of goodwill by reportable segment and in total which includes a rollforward schedule.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13854-109267
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