| **BORROWINGS (Tables)**                          | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 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| SHUSA                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         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| **Debt Instrument [Line Items]**                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  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| Schedule of Borrowings and Other Debt Obligation | The following table presents information regarding the Holding Company's borrowings and other debt obligations at the dates indicated: September 30, 2015 December 31, 2014 Balance EffectiveRate Balance EffectiveRate (dollars in thousands)3.00% senior notes, due September 2015$— —% $598,788 3.28%4.625% senior notes, due April 2016 475,467 4.85% 474,718 4.85%3.45% senior notes, due August 2018497,604 3.62% 497,025 3.62%2.65% senior notes, due April 2020992,211 2.83% — —%4.50% senior notes, due July 20251,093,824 4.57% — —%Junior subordinated debentures - Capital Trust VI, due June 203669,768 7.91% 69,751 7.91%Common securities - Capital Trust VI10,000 7.91% 10,000 7.91%Junior subordinated debentures - Capital Trust IX, due July 2036149,397 2.09% 149,375 2.04%Common securities - Capital Trust IX4,640 2.09% 4,640 2.04%     Total holding company borrowings and other debt obligations$3,292,911 3.91% $1,804,297 3.89%                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             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| Santander Bank                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         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| **Debt Instrument [Line Items]**                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  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| Schedule of Borrowings and Other Debt Obligation | The following table presents information regarding the Bank's borrowings and other debt obligations at the dates indicated:  September 30, 2015 December 31, 2014 Balance EffectiveRate Balance EffectiveRate (dollars in thousands)2.00% senior notes, due January 2018$745,485 2.27% $— —%Senior notes, due January 2018(1)249,187 1.31% — —%8.750% subordinated debentures, due May 2018498,008 8.92% 497,530 8.92%FHLB advances, maturing through August 201813,335,000 1.36% 9,455,000 2.06%Subordinated term loan, due February 2019130,678 6.15% 139,180 6.00%REIT (2) preferred, due May 2020154,550 13.54% 153,417 13.64%Subordinated term loan, due August 202230,867 7.89% 31,428 7.77%     Total Bank borrowings and other debt obligations$15,143,775 1.83% $10,276,555 2.64%(1) These notes will bear interest at a rate equal to the three-month London Interbank Offered Rate ("LIBOR") plus 93 basis points per annum.(2) Real estate investment trust ("REIT")                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        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| SCUSA                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         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| **Debt Instrument [Line Items]**                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  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| Schedule of Borrowings and Other Debt Obligation | The following tables present information regarding SCUSA's credit facilities as of September 30, 2015 and December 31, 2014: September 30, 2015 Balance EffectiveRate Assets Pledged Restricted Cash Pledged (dollars in thousands)Warehouse line, maturing on various dates(1)$698,715 1.26% $1,001,601 $39,046Warehouse line, maturing on various dates(2)1,087,977 1.36% 1,565,626 55,126Warehouse line, due October 2015(3)199,680 2.10% 261,042 9,433Warehouse line, due June 2016397,021 1.18% 544,546 —Warehouse line, due November 2016(4)175,000 1.76% — —Warehouse line, due November 2016(4)250,000 1.76% — 2,501Warehouse line, due March 2017510,899 0.94% 752,083 22,528Warehouse line, due July 2017(5)874,320 1.18% 1,006,388 34,531Warehouse line, due July 2017(6)1,608,643 1.17% 2,481,681 30,818Repurchase facility, due December 2015(7)851,929 1.87% 1,966 37,844Line of credit with related party, due December 2016(8)500,000 2.51% — —Line of credit with related party, due December 2016(8)1,750,000 2.48% — —Line of credit with related party, due December 2018(8)975,000 2.89% — —     Total SCUSA revolving credit facilities$9,879,184 1.76% $7,614,933 $231,827(1) Half of the outstanding balance on this facility matures in March 2016 and half matures in March 2017.(2) In December 2016, $500.0 million of the total revolving commitment under this warehouse line will expire, at which time any utilized balance attributable to that portion of the commitment will become an amortizing obligation; the remainder of the commitment of $2.0 billion matures in June 2017.(3) This line is held exclusively for personal term loans. On October 26, 2015, the maturity date for this warehouse line commitment was extended to November 9, 2015.(4) These lines are collateralized by residuals retained by SCUSA.(5) This line is held exclusively for financing Chrysler loans.(6) This line is held exclusively for financing Chrysler leases.(7) The repurchase facility is collateralized by securitization notes payable retained by SCUSA. No portion of this facility is unsecured. This facility has rolling 30-day and 90 -day maturities.(8) These lines are also collateralized by securitization notes payable and residuals retained by SCUSA. As of September 30, 2015, $2.5 billion of the aggregate outstanding balances on these credit facilities was unsecured.NOTE 10. BORROWINGS (continued) December 31, 2014 Balance EffectiveRate Assets Pledged Restricted Cash Pledged (dollars in thousands)Warehouse line, maturing on various dates(1)$397,452 1.26% $589,529 $20,661Warehouse line, due March 2015(2)250,594 0.98% — —Warehouse line, due June 2015243,736 1.17% 344,822 —Warehouse line, due September 2015(3)199,980 1.96% 351,755 13,169Warehouse line, due December 2015468,565 0.93% 641,709 16,467Warehouse line, due June 2016(4)2,201,511 0.98% 3,249,263 65,414Warehouse line, due June 20161,051,777 1.06% 1,481,135 28,316Warehouse line, due October 2016(3)240,487 2.02% 299,195 17,143Warehouse line, due November 2016(5)175,000 1.71% — —Warehouse line, due November 2016(5)250,000 1.71% — 2,500Repurchase facility, maturing on various dates(6)923,225 1.63% — 34,184Line of credit with related party, due December 2016(7)500,000 2.46% 1,340 —Line of credit with related party, due December 2016(7)1,750,000 2.33% — —Line of credit with related party, due December 2018(7)1,140,000 2.85% 9,701 —     Total SCUSA revolving credit facilities$9,792,327 1.68% $6,968,449 $197,854(1) Half of the outstanding balance on this facility had maturity dates in March 2015 and half matures in March 2016.(2) This line is collateralized by securitization notes payable retained by SCUSA.(3) These lines are held exclusively for personal consumer term loans.(4) This line is held exclusively for Chrysler Capital retail loan and lease financing.(5) These lines are collateralized by residuals retained by SCUSA.(6) The repurchase facility is collateralized by securitization notes payable retained by SCUSA. No portion of this facility is unsecured. This facility has rolling 30-day and 90-day maturities.(7) These lines are also collateralized by securitization notes payable and residuals retained by SCUSA. As of December 31, 2014, $2.2 billion of the aggregate outstanding balances on these credit facilities was unsecured.The following tables present information regarding SCUSA's secured structured financings as of September 30, 2015 and December 31, 2014: September 30, 2015 Balance Initial Note Amounts Issued Initial Weighted Average Interest Rate Range Collateral Restricted Cash (dollars in thousands)SCUSA public securitizations, maturing on various dates(1)$13,377,986 $23,863,842 0.89% - 2.29% $16,852,670 $1,194,363SCUSA privately issued amortizing notes, maturing on various dates(1)6,677,464 10,174,679 0.88% - 1.62% 9,831,162 368,134     Total SCUSA secured structured financings$20,055,450 $34,038,521 0.88% - 2.29% $26,683,832 $1,562,497NOTE 10. BORROWINGS (continued) December 31, 2014 Balance Initial Note Amounts Issued Initial Weighted Average Interest Rate Range Collateral Restricted Cash (dollars in thousands)SCUSA public securitizations, maturing on various dates(1)$11,523,729 $26,682,930 0.89% - 2.80% $14,345,242 $1,184,047SCUSA privately issued amortizing notes, maturing on various dates(1)6,282,474 8,499,111 1.05% - 1.85% 9,114,997 281,038     Total SCUSA secured structured financings$17,806,203 $35,182,041 0.89% - 2.80% $23,460,239 $1,465,085(1) SCUSA has entered into various securitization transactions involving its retail automotive installment loans and leases. These transactions are accounted for as secured financings and therefore both the securitized retail installment contracts and the related securitization debt issued by SPEs, remain on the Condensed Consolidated Balance Sheet. The maturity of this debt is based on the timing of repayments from the securitized assets. |

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| - Definition
Tabular disclosure of information pertaining to short-term and long-debt instruments or arrangements, including but not limited to identification of terms, features, collateral requirements and other information necessary to a fair presentation.
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