|**GOODWILL AND OTHER INTANGIBLES (Tables)**                             | 6 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 reportable segments for thesix-month period endedJune 30, 2016:Consumer and Business Banking(1)Auto Finance & Business BankingCommercial Real Estate(2)Commercial Banking(2)Global Corporate BankingSCTotal(in thousands)Goodwill at December 31, 2015$1,550,321$445,923$—$1,297,055$131,130$1,019,960$4,444,389Disposals during the period———————Additions during the period———————Impairment during the period———————Re-allocations during the period329,983(445,923)870,411(754,471)———Goodwill at June 30, 2016$1,880,304$—$870,411$542,584$131,130$1,019,960$4,444,389(1)  Consumer and Business Banking were formerly designated as the Retail Banking segment and was renamed during the first quarter of 2016.(2)  Commercial Real Estate and Commercial Banking were formerly disclosed as the combined Real Estate and Commercial Banking segment.                                                                         
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|Goodwill at December 31, 2015                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Disposals during the period                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Additions during the period                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Impairment during the period                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Re-allocations during the period                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Goodwill at June 30, 2016                                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|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.June 30, 2016December 31, 2015NetCarryingAmountAccumulatedAmortizationNetCarryingAmountAccumulatedAmortization(in thousands)Intangibles subject to amortization:Dealer networks$485,232$(94,768)$504,839$(75,161)Chrysler relationship102,500(36,250)110,000(28,750)Core deposit intangibles—(295,842)763(295,079)Trade name(1)17,700(300)——Other intangibles3,924(25,985)5,453(24,455)Total intangibles subject to amortization609,356(453,145)621,055(423,445)Intangibles not subject to amortization:Trade name(1)——18,000—Total Intangibles$609,356$(453,145)$639,055$(423,445)(1)As ofDecember 31, 2015, the trade name intangible asset was identified as an indefinite-lived intangible not subject to amortization. EffectiveApril 1, 2016, management has determined this asset to be a definite-lived intangible with a remaining useful life of15 years.
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|                                                                        | June 30, 2016                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|                                                                        | NetCarryingAmount                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|                                                                        | (in thousands)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Intangibles subject to amortization:                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Dealer networks                                                         | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Chrysler relationship                                                   | 102,500                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Core deposit intangibles                                                | —                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Trade name(1)                                                           | 17,700                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Other intangibles                                                       | 3,924                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
|Total intangibles subject to amortization                               | 609,356                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
|Intangibles not subject to amortization:                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Trade name(1)                                                           | —                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Total Intangibles                                                       | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Schedule of Finite-Lived Intangible Assets, Future Amortization Expense | The estimated aggregate amortization expense related to intangibles, excluding any impairment charges, for each of the five succeeding calendar years ending December 31 is:YearCalendar Year AmountRecorded To DateRemaining Amount To Record(in thousands)2016$58,062$29,699$28,363201756,255—56,255201855,902—55,902201955,701—55,701202055,641—55,641Thereafter357,494—357,494                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
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|Year                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
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|2016                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|2017                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|2018                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|2019                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|2020                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Thereafter                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             

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