Significant Accounting Policies	6 Months Ended
Significant Accounting Policies	Jun. 30, 2019
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies Basis of Presentation The accompanying unaudited, consolidated financial statements of SLM Corporation (“Sallie Mae,” “SLM,” the “Company,” “we,” or “us”) have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) for interim financial information. Accordingly, they do not include all the information and footnotes required by GAAP for complete consolidated financial statements. The consolidated financial statements include the accounts of SLM Corporation and its majority-owned and controlled subsidiaries after eliminating the effects of intercompany accounts and transactions. In the opinion of management, all adjustments considered necessary for a fair statement of the results for the interim periods have been included. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. Operating results for the three and six months ended June 30, 2019 are not necessarily indicative of the results for the year ending December 31, 2019 or for any other period. These unaudited financial statements should be read in conjunction with the audited financial statements and related notes included in our Annual Report on Form 10-K for the year ended December 31, 2018 (the “2018 Form 10-K”). Consolidation The consolidated financial statements include the accounts of the Company and its majority-owned and controlled subsidiaries after eliminating the effects of intercompany accounts and transactions. We consolidate any variable interest entity (“VIE”) where we have determined we are the primary beneficiary. The primary beneficiary is the entity which has both: (1) the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and (2) the obligation to absorb losses or receive benefits of the entity that could potentially be significant to the VIE. Reclassifications Certain reclassifications have been made to the balances for the three and six months ended June 30, 2018, to be consistent with classifications adopted in 2019, which had no effect on net income, total assets or total liabilities. Recently Issued and Adopted Accounting Pronouncements ASU No. 2016-02, “Leases” In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-02, “Leases,” a comprehensive new lease standard which supersedes previous lease guidance. The standard requires a lessee to recognize in its balance sheet assets and liabilities related to long-term leases that were classified as operating leases under previous guidance. An asset will be recognized related to the right to use the underlying asset and a liability will be recognized related to the obligation to make lease payments over the term of the lease. The standard also requires expanded disclosures surrounding leases. The standard is effective for fiscal periods beginning after December 15, 2018, and requires modified retrospective adoption, with early adoption permitted. We adopted this guidance on January 1, 2019. In doing so, we identified and evaluated the related lease contracts and revised our controls and processes to address the lease standard. The adoption of this guidance resulted in the recognition of less than $34 million of right of use asset and lease liability, which did not have a material impact on our consolidated financial statements. Recently Issued but Not Yet Adopted Accounting Pronouncements ASU No. 2016-13, “Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments” In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments,” which will become effective for us on January 1, 2020. This ASU eliminates the current accounting guidance for the recognition of credit impairment. Under the new guidance, for all loans carried at amortized cost, upon loan origination we will be required to measure our allowance for loan losses based on our estimate of all current expected credit losses (“CECL”) over the remaining contractual term of the assets. Updates to that estimate each period will be recorded through provision expense. The estimate of loan losses must be based on historical experience, current conditions, and reasonable and supportable forecasts. The ASU does not mandate the use of any specific method for estimating credit loss, permitting companies to use judgment in selecting the approach that is most appropriate in their circumstances. Upon adoption, a cumulative effect adjustment to retained earnings will be recorded as of the beginning of the first reporting period in which the guidance is effective in an amount necessary to adjust the allowance for loan losses to equal the current estimate of expected losses on financial assets held at that date. We have evaluated the standard and initiated implementation efforts. We have identified the loss forecasting approach and have built the loss models for our Private Education Loans (as hereinafter defined) and our Personal Loans (as hereinafter defined) acquired from third-parties. For our Private Education Loan and total Personal Loan portfolios, we will be using the discounted cash flow approach to calculate our current expected credit losses. We estimate the CECL allowance using relevant available information, from internal and external sources, relating to past events, current conditions, and reasonable and supportable forecasts. We have determined that, for modeling current expected credit losses, we can reasonably estimate expected losses that incorporate the current and forecasted economic conditions over a two-year period, after which the model will immediately revert to our long-term expected loss rates. During the remainder of 2019, we plan to complete our loss models for Personal Loans we originate and credit card receivables and complete the testing and validation for all the models to be used to implement CECL. During the second quarter of 2019, we performed a dry run of our CECL solution for our Private Education Loan and purchased Personal Loan portfolios to test the end-to-end implementation of the new solution. The loss and other models that will be used in our CECL solution are currently undergoing validation or will be in the coming months. Adoption of the standard will have a material impact on how we record and report our financial condition and results of operations, and on regulatory capital. The extent of the impact upon adoption at January 1, 2020 will likely depend on the characteristics of our loan portfolio and economic conditions at that date, as well as forecasted conditions thereafter.