| **BASIS OF PRESENTATION AND ACCOUNTING POLICIES (Policies)**      | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|-------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
||
| **Accounting Policies [Abstract]**                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| Basis of Presentation                                             | Basis of PresentationThese Condensed Consolidated Financial Statements include the accounts of the Company and its subsidiaries, including the Bank, SCUSA, and certain special purpose financing trusts utilized in financing transactions that are considered variable interest entities ("VIEs"). The Company consolidates VIEs for which it is deemed the primary beneficiary. The Condensed Consolidated Financial Statements have been prepared by the Company, without audit, pursuant to SEC regulations. All intercompany balances and transactions have been eliminated in consolidation. Additionally, where applicable, the Company's accounting policies conform to the accounting and reporting guidelines prescribed by bank regulatory authorities. However, in the opinion of management, the accompanying unaudited Condensed Consolidated Financial Statements reflect all adjustments of a normal and recurring nature necessary to present fairly the Condensed Consolidated Balance Sheets, Condensed Statements of Operations, Condensed Statements of Comprehensive Income, Condensed Statements of Stockholder's Equity and Condensed Statements of Cash Flows for the periods indicated, and contain adequate disclosure to make the information presented not misleading.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| Reclassifications and Corrections to Previously Reported Amounts  | Reclassifications and Corrections to Previously Reported AmountsCertain prior year amounts have been reclassified to conform to the current year presentation. These reclassifications did not have an impact on the consolidated financial condition or results of operations. The Company has made certain corrections to the September 30, 2014 Condensed Consolidated Statements of Cash Flows and Note 5 thereto. The Company identified and corrected immaterial classification errors with respect to certain cash flows related to loans held for investment, Federal Home Loan Bank ("FHLB") advance repayments and short-term borrowings reported within cash flows in financing activities, as well as classification errors related to certain restricted cash accounts within investing activities. Certain cash flows related to decreases in deferred tax assets have been reclassified from net changes in other liabilities to net changes in other assets within operating cash flows. These changes resulted in increased total cash provided by operating activities and increased total cash used in investing activities by an equal and offsetting amount. There was no net impact to cash provided by financing activities. The reclassification errors did not impact the net change in cash and cash equivalents, total cash and cash equivalents, net income, or any other operating measure.The corrections to Note 5 related to the components of troubled debt restructuring ("TDR") activities for the three-month and nine-month periods endedSeptember 30, 2014. The corrections do not affect the Condensed Consolidated Statements of Operations, Condensed Consolidated Statements of Comprehensive Income for the three-month and nine-month periods endedSeptember 30, 2015 and 2014, the Condensed Consolidated Statements of Stockholder's Equity for the nine-month periods endedSeptember 30, 2015 and 2014, or the Condensed Consolidated Balance Sheets at September 30, 2015 and 2014.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| Changes in Accounting Policies and Recent Accounting Developments | Changes in Accounting Policies  During the first quarter of 2015, the Company adopted the following Financial Accounting Standards Board (the "FASB") Accounting Standards Updates ("ASUs"), none of which had a material impact to the Company's Condensed Consolidated financial statements: •The Company adopted the FASB ASU 2014-01, Investments - Equity Method and Joint Ventures (Topic 323): Accounting for Investments in Qualified Affordable Housing Projects, which allows an entity to make an accounting policy election toaccount for its investments in qualified affordable housing projects using the proportional amortization method, if certain conditions are met. Under this method, an investor would amortize the cost of its investments in proportion to the tax credits and other tax benefits received and will recognize the amortization, net of tax credits and other tax benefits, in the income statement as a component of income tax expense. This ASU is required to be adopted on a retrospective basis for all periods presented. The adoption of this ASU did not have a material effect to the Company’s prior periods’ consolidated financial statements to warrant retrospective application. The cumulative effect of the adoption was recognized in the first quarter of 2015 and was not material to the Company’s Condensed Consolidated Financial Statements. •The Company adopted FASB ASU 2014-04, Receivables - Troubled Debt Restructurings by Creditors (Subtopic 310-40) - Reclassification of Residential Real Estate Collateralized Consumer Mortgage Loans upon Foreclosure, on a prospective basis. Under this ASU, an in-substance repossession or foreclosure occurs when the creditor obtains legal title to the residential real estate property or the borrower conveys all interest in the residential real estate property to the creditor to satisfy the loan through completion of a deed in lieu of foreclosure or through a similar legal agreement. The Company’s adoption of this ASU did not have a material effect on its Condensed Consolidated Financial Statements. •The Company adopted FASB ASU 2014-14, Receivables - Troubled Debt Restructurings by Creditors (Subtopic 310-40): Classification of Certain Government-Guaranteed Mortgage Loans upon Foreclosure. This ASU requires that a government-guaranteed mortgage loan be de-recognized, and that a separate other receivable be recognized, upon foreclosure if the three criteria identified in the ASU are met. Upon foreclosure and meeting the three criteria, the separate other receivable should be measured based on the amount of the loan balance (principal and interest) that is expected to be recovered from the guarantor. The Company’s adoption of this ASU did not have a material effect on its Condensed Consolidated Financial Statements. •During the third quarter of 2015, the Company early adopted FASB ASU 2015-03, Interest- Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs, on a retrospective basis. This ASU simplifies the presentation of debt issuance costs and requires that debt issuance costs be presented as a deduction from the recognized debt liability, and eliminates prior guidance which required that debt issuance costs be recorded as a deferred charge.In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606), superseding the revenue recognition requirements in ASC 605. This ASU requires an entity to recognize revenue for the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The amendment includes a five-step process to assist an entity in achieving the main principle(s) of revenue recognition under ASC 605. In August 2015, the FASB issued ASU 2015-14, which formalized the deferral of the effective date of the amendment for a period of one-year from the original effective date. Following the issuance of ASU 2015-14, the amendment will be effective for the Company for the first annual period ending after December 15, 2017. The amendment should be applied retrospectively to each prior reporting period presented or as a cumulative effect adjustment as of the date of adoption. Early adoption of the guidance is not permitted. The Company is currently evaluating the impact of adopting this ASU on its financial position, results of operations and disclosures.In June 2014, the FASB issued ASU 2014-12, Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period (Topic 718). This ASU requires that a performance target that affects vesting, and could be achieved after the requisite service period, be treated as a performance condition. Application of existing guidance in ASC 718 as it relates to awards with performance conditions that affect vesting should continue to be used to account for such awards. The amendment will be effective for the Company for the first reporting period ending after December 15, 2015. Adoption of this amendment should be applied on a prospective basis to awards that are granted or modified on or after the effective date. There also is an option to apply the amendments on a modified retrospective basis for performance targets outstanding on or after the beginning of the first annual period presented as of the adoption date. Early adoption is permitted. The Company is currently evaluating the impact of adopting this ASU on its financial position, results of operations and disclosures.In August 2014, the FASB also issued ASU 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (Subtopic 205-40). This ASU requires management to perform an assessment of going concern and provides specific guidance on when and how to assess or disclose going concern uncertainties. The new standard also defines terms used in the evaluation of going concern, such as "substantial doubt." Following application, the Company will be required to perform assessments at each annual and interim period, provide an assessment period of one year from the issuance date, and make disclosures in certain circumstances in which substantial doubt is identified. The amendment will be effective for the Company for the first reporting period ending after December 15, 2016. Earlier application is permitted. The Company does not expect the adoption of this ASU to have an impact on its financial position, result of operations, or disclosures. In January 2015, the FASB issued ASU 2015-01, Income Statement - Extraordinary and Unusual Items (Subtopic 225-20): Simplifying Income Statement Presentation by Eliminating the Concept of Extraordinary Items. This ASU eliminates the concept of extraordinary items from GAAP, which previously required the separate classification, presentation, and disclosure of extraordinary events and transactions. The amendment will be effective for the Company for the first reporting period ending after December 15, 2015, with early adoption permitted if the guidance is applied from the beginning of the fiscal year of adoption. Adoption of the amendment by the Company can be either on a prospective or retrospective basis. The Company plans to apply this amendment effective for reporting periods beginning after December 15, 2015 and will apply it prospectively, as the Company has not reported any extraordinary items in the three prior fiscal years. The Company does not expect the adoption of this ASU to have an impact on its financial position, results of operations, or disclosures. In February 2015, the FASB issued ASU 2015-02, Consolidation (Topic 820): Amendments to the Consolidation Analysis. This ASU changes the analysis that a reporting entity must perform to determine whether it should consolidate certain types of legal entities. The amendment will be effective for the Company for the first reporting period ending after December 15, 2015, with early adoption permitted if the guidance is applied from the beginning of the fiscal year of adoption. Adoption of the amendment by the Company may be on a retrospective or modified retrospective basis. The Company is in the process of evaluating the impacts of the adoption of this ASU. NOTE 2. RECENT ACCOUNTING DEVELOPMENTS (continued)In May 2015, the FASB issued ASU 2015-7, Fair Value Measurement (Topic 820): Disclosures for Investments in Certain Entities that Calculate Net Asset Value per Share (or Its Equivalent) (a consensus of the Emerging Issues Task Force). This ASU removes the requirement to categorize investments fair valued using the net asset value per share practical expedient within the fair value hierarchy. It also modifies disclosure requirements to include only investments for which the entity elects to use the practical expedient rather than the prior guidance which required disclosures for all investments eligible to use the practical expedient. This amendment will be effective for the Company for the first reporting period beginning after December 15, 2015, with early adoption permitted. Adoption of the amendment by the Company must be on a retrospective basis for all periods presented. The Company is in the process of evaluating the impacts of the adoption of this ASU. In September 2015, the FASB issued ASU 2015-16, Business Combinations (Topic 805): Simplifying the Accounting for Measurement Period Adjustments. This amendment eliminates the requirement to retrospectively account for adjustments to provisional amounts recognized in a business combination. Instead, the acquirer will recognize the adjustments to provisional amounts during the period in which the adjustments are determined, including the effect on earnings of any amounts the acquirer would have recorded in previous periods if the accounting had been completed at the acquisition date. This amendment will be effective for the Company for the first reporting period beginning after December 15, 2015, with earlier adoption permitted for financial statements that have not been issued. Adoption of the amendment by the Company must be on a prospective basis to adjustments to provisional amounts that occur after the effective date. The Company does not expect the adoption of this ASU to have an impact on its financial position, results of operations, or disclosures. |
| Use of Estimates                                                  | Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The most significant estimates pertain to consolidation, fair value measurements, allowance for loan and lease losses and reserve for unfunded lending commitments, estimates of expected residual values of leased vehicles subject to operating leases, goodwill, derivatives and hedge activities, and income taxes. Actual results may differ from the estimates, and the differences may be material to the Condensed Consolidated Financial Statements.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| Subsequent Events                                                 | Subsequent Events The Company evaluated events from the date of the Condensed Consolidated Financial Statements on September 30, 2015 through the issuance of these Condensed Consolidated Financial Statements and has determined that there have been no material events that would require recognition in its Condensed Consolidated Financial Statements or disclosure in the Notes to the Condensed Consolidated Financial Statements for the quarter ended September 30, 2015 other than the transactions disclosed within Note 5 of these Condensed Consolidated Financial Statements.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| Troubled Debt Restructurings                                      | Commercial Loan TDRsAll of the Company’s commercial loan modifications are based on the circumstances of the individual customer, including specific customers' complete relationship with the Company. Loan terms are modified to meet each borrower’s specific circumstances at a point in time. Modifications for commercial loan TDRs generally, although not always, result in bifurcation of the original loan into A and B notes. The A note is restructured to allow for upgraded risk rating and return to accrual status after a sustained period of payment performance has been achieved (typically six months for monthly payment schedules). The B note, if any, is structured as a deficiency note; the balance is charged off but the debt is usually not forgiven. As TDRs, they will be subject to analysis for specific reserves by either calculating the present value of expected future cash flows or, if collateral-dependent, calculating the fair value of the collateral less its estimated cost to sell. The TDR classification will remain on the loan until it is paid in full or liquidated.NOTE 5. LOANS AND ALLOWANCE FOR CREDIT LOSSES (continued)Consumer Loan TDRsThe primary modification program for the Company’s residential mortgage and home equity portfolios is a proprietary program designed to keep customers in their homes and, when appropriate, prevent them from entering into foreclosure. The program is available to all customers facing a financial hardship regardless of their delinquency status. The main goal of the modification program is to review the customer’s entire financial condition to ensure that the proposed modified payment solution is affordable according to a specific debt-to-income ("DTI") ratio range. The main modification benefits of the program allow for term extensions, interest rate reductions, and/or deferment of principal. The Company reviews each customer on a case-by-case basis to determine which benefit or combination of benefits will be offered to achieve the target DTI range.For the Company’s other consumer portfolios, including retail installment contracts and autos, the terms of the modifications generally include one or a combination of the following: a reduction of the stated interest rate of the loan at a rate of interest lower than the current market rate for new debt with similar risk or an extension of the maturity date.Consumer TDRs are generally placed on non-accrual status until the Company believes repayment under the revised terms is reasonably assured and a sustained period of repayment performance has been achieved (typically six months for a monthly amortizing loan). Any loan that has remained current for the six months immediately prior to modification will remain on accrual status after the modification is enacted. Exceptions to this policy include retail installment contracts, which may begin accruing as soon as they are made current. The TDR classification will remain on the loan until it is paid in full or liquidated.In addition to those identified as TDRs above, the guidance also requires loans discharged under Chapter 7 bankruptcy to be considered TDRs and collateral-dependent, regardless of delinquency status. These loans must be written down to fair market value and classified as non-accrual/non-performing for the remaining life of the loan. During the quarter ended September 30, 2015, the Company reassessed its TDR definition and has determined that certain modifications should not be reported as a TDR.  An example of that are retail installment contracts that have received modifications under the Service members Civil Relief Act (the "SCRA"). The inclusion of these modified loans were not material to prior periods.TDR Impact to Allowance for Loan LossesThe allowance for loan losses is established to recognize losses inherent in funded loans intended to be held for investment that are probable and can be reasonably estimated. Prior to loans being placed in TDR, the Company generally measures its allowance under a loss contingency methodology in which consumer loans with similar risk characteristics are pooled and loss experience information is monitored for credit risk and deterioration with statistical tools considering factors such as delinquency, LTV and credit scores.Upon TDR modification, the Company generally measures impairment based on a present value of expected future cash flows methodology considering all available evidence using the effective interest rate or fair value of collateral. The amount of the required valuation allowance is equal to the difference between the loan’s impaired value and the recorded investment.When a consumer TDR subsequently defaults, the Company generally measures impairment based on the fair value of the collateral, if applicable, less its estimated cost to sell.Typically, commercial loans whose terms are modified in a TDR will have been identified as impaired prior to modification and accounted for generally using a present value of expected future cash flows methodology, unless the loan is considered collateral-dependent. Loans considered collateral-dependent are measured for impairment based on their fair values of collateral less its estimated cost to sell. Accordingly, upon TDR modification or if a TDR modification subsequently defaults, the allowance methodology remains unchanged.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| Commercial Lending Asset Quality Indicators                       | Commercial Lending Asset Quality IndicatorsCommercial credit quality disaggregated by class of financing receivables is summarized according to standard regulatory classifications as follows:PASS. Asset is well-protected by the current net worth and paying capacity of the obligor or guarantors, if any, or by the fair value less costs to acquire and sell any underlying collateral in a timely manner.SPECIAL MENTION. Asset has potential weaknesses that deserve management’s close attention, which, if left uncorrected, may result in deterioration of the repayment prospects for an asset at some future date. Special Mention assets are not adversely classified.SUBSTANDARD. Asset is inadequately protected by the current net worth and paying capacity of the obligor or by the collateral pledged, if any. A well-defined weakness or weaknesses exist that jeopardize the liquidation of the debt. The loans are characterized by the distinct possibility that the Bank will sustain some loss if deficiencies are not corrected.DOUBTFUL. Exhibits the inherent weaknesses of a substandard credit. Additional characteristics exist that make collection or liquidation in full highly questionable and improbable, on the basis of currently known facts, conditions and values. Possibility of loss is extremely high, but because of certain important and reasonable specific pending factors which may work to the advantage and strengthening of the credit, an estimated loss cannot yet be determined.LOSS. Credit is considered uncollectible and of such little value that it does not warrant consideration as an active asset. There may be some recovery or salvage value, but there is doubt as to whether, how much or when the recovery would occur.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |

| X                                                                                                                                                                                                                                                                                                                 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Policy of credit quality indicators used for commercial and consumer loans.
+ References
No definition available.
+ Details**Name:**sov_CreditQualityOfFinancingReceivablesPolicyTextBlock**Namespace Prefix:**sov_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - References
No definition available.
+ Details**Name:**us-gaap_AccountingPoliciesAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Disclosure of accounting policy for basis of accounting, or basis of presentation, used to prepare the financial statements (for example, US Generally Accepted Accounting Principles, Other Comprehensive Basis of Accounting, IFRS).
+ References
No definition available.
+ Details**Name:**us-gaap_BasisOfAccountingPolicyPolicyTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Disclosure of the accounting policy for loan agreements whose terms have been modified because of the inability of the borrower for financial reasons to comply with the terms of the original loan agreement. A creditor discloses material facts pertaining to significant modifications.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 40 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=25495931&loc=d3e18794-111554Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=51655414&loc=d3e18780-107790
+ Details**Name:**us-gaap_LoansAndLeasesReceivableTroubledDebtRestructuringPolicy**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Disclosure of accounting policy pertaining to new accounting pronouncements that may impact the entity's financial reporting. Includes, but is not limited to, quantification of the expected or actual impact.
+ References
No definition available.
+ Details**Name:**us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Disclosure of accounting policy for reclassifications that affects the comparability of the financial statements.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6359566&loc=d3e326-107755
+ Details**Name:**us-gaap_PriorPeriodReclassificationAdjustmentDescription**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Disclosure of accounting policy for reporting subsequent events.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=51655414&loc=d3e18780-107790
+ Details**Name:**us-gaap_SubsequentEventsPolicyPolicyTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Disclosure of accounting policy for the use of estimates in the preparation of financial statements in conformity with generally accepted accounting principles.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=51801978&loc=d3e6061-108592Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=51801978&loc=d3e6143-108592Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=51801978&loc=d3e6132-108592
+ Details**Name:**us-gaap_UseOfEstimates**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |