| **REGULATORY MATTERS (Tables)**                           | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
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| **Banking and Thrift [Abstract]**                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Schedule of Actual Capital Balances of the Bank and SHUSA | The following schedule summarizes the actual Basel I capital balances of the Bank and SHUSA at December 31, 2013 and 2012:  REGULATORY CAPITAL  Tier 1 LeverageCapital Ratio Tier 1 Risk-BasedCapital Ratio Total Risk-BasedCapital Ratio Tier 1 Common Capital Ratio(1) ($ in thousands)Santander Bank at December 31, 2013:        Regulatory capital $8,390,428 $8,390,428 $9,550,558 $8,390,428Capital ratio 12.09% 13.96% 15.89% 13.96%SHUSA at December 31, 2013 (2)(3):        Regulatory capital $9,210,100 $9,210,100 $10,555,146 $8,794,393Capital ratio 12.78% 14.67% 16.81% 14.01%Santander Bank at December 31, 2012:        Regulatory capital $8,027,173 $8,027,173 $9,310,905 $8,027,173Capital ratio 10.52% 12.86% 14.92% 12.86%SHUSA at December 31, 2012 (2):        Regulatory capital $8,496,977 $8,496,977 $10,116,806 $8,075,995Capital ratio 10.79% 13.08% 15.57% 12.43% (1)Ratio presented due to regulators emphasizing the Tier 1 common capital ratio in their evaluation of bank and BHC capital levels, although this metric is not provided for in bank regulations. For all BHCs undergoing its Comprehensive Capital Analysis and Review, the Federal Reserve has established a 5% minimum Tier 1 common capital ratio under stress scenarios.(2)Ratios have been determined using SHUSA's current accounting method for SCUSA as an equity method investment.(3)The consolidation of SCUSA (as described in Note 6) will have an impact to SHUSA's regulatory capital ratios during the first quarter. |

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| - Definition
Tabular disclosure of the capital amounts and ratios as of the balance sheet date, indicating whether the entity or entities are in compliance with regulatory capital requirements, by entity.
+ References
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