Receivables [Abstract] Allowance for credit losses and recorded investments in loans Allowance for Credit Losses on Financing Receivables [Table Text Block] Impaired financing receivables Impaired Financing Receivables [Table Text Block] Average recorded investment and interest income recognized for troubled debt restructuring loans Average Recorded Investment And Interest Income Recognized For Troubled Debt Restructuring Loans [Table Text Block] Average Recorded Investment And Interest Income Recognized For Troubled Debt Restructuring Loans [Table Text Block] Age analysis of past due loans delinquencies Past Due Financing Receivables [Table Text Block] Modified loans accounts for troubled debt restructuring Modified Loans Accounts For Troubled Debt Restructuring [Table Text Block] Modified Loans Accounts For Troubled Debt Restructuring [Table Text Block] Private education loan portfolio stratified by key credit quality indicators Financing Receivable Credit Quality Indicators [Table Text Block] Accrued interest receivable Accrued Interest Receivable [Table Text Block] Accrued interest receivable. Total Interest Receivable Accrued Interest Receivable On Private Education Loans Accrued interest receivable on private education loans. Greater Than 90 Days Past Due Greater Than Ninety Days Past Due Accrued Interest Receivable Greater than ninety days past due accrued interest receivable. Allowance for Uncollectible Interest Allowance For Uncollectible Accrued Interest Allowance For Uncollectible Accrued Interest Banking and Thrift [Abstract] Schedule of deposits Schedule of Deposits [Table Text Block] Schedule of Deposits [Table Text Block] Interest bearing deposits Interest Bearing Deposits [Table Text Block] [Table Text Block] for Interest Bearing Deposits [Table] Fair Value Disclosures [Abstract] Valuation of financial instruments that are marked-to-market on recurring basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Fair Values of financial assets and liabilities, including derivative financial instruments Fair Value, by Balance Sheet Grouping [Table Text Block] Regulatory Capital Regulatory Capital Requirements under Banking Regulations [Text Block] Equity [Abstract] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Common Stock Common Stock [Member] Class of Stock [Line Items] Class of Stock [Line Items] Common stock closing price (in dollars per share) Share Price Debt Disclosure [Abstract] Securities Financing Transaction [Table] Securities Financing Transaction [Table] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] LIBOR London Interbank Offered Rate (LIBOR) [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] 2015-B Issuance 2015-B [Member] Issuance 2015-B [Member] 2016-A Issuance 2016-A [Member] Issuance 2016-A [Member] 2016-B Issuance 2016-B [Member] Issuance 2016-B [Member] 2016-C Issuance 2016-C [Member] Issuance 2016-C [Member] 2017-A Issuance 2017 - A [Member] Issuance 2017 - A [Member] Securities Financing Transaction [Line Items] Securities Financing Transaction [Line Items] Total Issued Debt Instrument, Face Amount Basis spread on variable rate Derivative, Basis Spread on Variable Rate Weighted Average Life (in years) Debt Instrument, Weighted Average Life Debt Instrument, Weighted Average Life Total loan and accrued interest amount securitized at inception on-balance sheet term securitization Loan Amount Securitized Loan Amount Securitized Percent of private loans indexed to LIBOR Percent of Private Loans indexed to LIBOR Percent of Private Loans indexed to LIBOR Tier 1 of government guarantee (in percentage) Tier One of Government Guarantee Tier One of Government Guarantee Tier 2 of government guarantee (in percentage) Tier Two of Government Guarantee Tier Two of Government Guarantee Tier 3 of government guarantee (in percentage) Tier Three of Government Guarantee Tier Three of Government Guarantee Estimated weighted average life of student loans (in years) Estimated Weighted Average Life Of Student Loans Estimated weighted average life of student loans. Schedule of debt Schedule of Debt [Table Text Block] Schedule of securities financing transactions Schedule of Securities Financing Transactions [Table Text Block] Schedule of variable interest entities Schedule of Variable Interest Entities [Table Text Block] Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Series A Preferred Stock Series A Preferred Stock [Member] Series B Preferred Stock Series B Preferred Stock [Member] Statement [Line Items] Statement [Line Items] Preferred stock dividend rate (in dollars per share) Preferred Stock, Dividend Rate, Per-Dollar-Amount Fair Value Measurements Fair Value Disclosures [Text Block] Derivative Instruments and Hedging Activities Disclosure [Abstract] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Interest rate swaps Interest Rate Swap [Member] Hedging Relationship [Axis] Hedging Relationship [Axis] Hedging Relationship [Domain] Hedging Relationship [Domain] Cash Flow Cash Flow Hedging [Member] Fair Value Fair Value Hedging [Member] Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Designated as Hedging Instrument Designated as Hedging Instrument [Member] Trading Not Designated as Hedging Instrument [Member] Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Derivative Assets Derivative Asset, Fair Value, Gross Asset Derivative Liabilities Derivative Liability, Fair Value, Gross Liability Total net derivatives Derivative Asset (Liability) Derivative Asset (Liability) Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Class of Financing Receivable [Axis] Class of Financing Receivable, Type [Axis] Class of Financing Receivable [Domain] Class of Financing Receivable, Type [Domain] Student Loan Student Loan [Member] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Domain] Financing Receivable Portfolio Segment [Domain] Consumer Portfolio Segment Consumer Portfolio Segment [Member] Financing Receivables, Period Past Due [Axis] Financing Receivables, Period Past Due [Axis] Financing Receivables, Period Past Due [Domain] Financing Receivables, Period Past Due [Domain] Loans delinquent 31-60 days Financing Receivables 31 to 60 Days Past Due [Member] Financing Receivables 31 to 60 Days Past Due [Member] Loans delinquent 61-90 days Financing Receivables, 61 to 90 Days Past Due [Member] Financing Receivables, 61 to 90 Days Past Due [Member] Loans delinquent, greater than 90 days Financing Receivables, Greater Than 90 Days Past Due [Member] Financing Receivables, Greater Than 90 Days Past Due [Member] Receivable Type [Axis] Receivable Type [Axis] Receivable Type [Domain] Receivable [Domain] Troubled Debt Restructured Loans Troubled Debt Restructured Loans [Member] Troubled Debt Restructured Loans [Member] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] TDR loans in in-school/grace/deferment Loan Status In School Grace And Deferment Recorded Investment Loan status in school grace and deferment recorded investment. TDR loans in forbearance Loan Status Forbearance Recorded Investment Loan status forbearance recorded investment. TDR loans in repayment and percentage of each status: Loans In Repayment And Percentage Of Each Status [Abstract] Loans in repayment and percentage of each status. Loans current Financing Receivable, Recorded Investment, Current Loans delinquent Financing Receivable, Recorded Investment, Past Due Total TDR loans in repayment Loans In Repayment Total loans in repayment. Total TDR loans, gross Loans Gross Total loans, gross Loans current (as a percentage) Loans In Repayment Current In Percentage Loans in repayment current in percentage. Loans delinquent (as a percentage) Financing Receivable, Percent Past Due Total TDR loans in repayment Loans In Repayment In Percentage Total loans in repayment, in percentage. Dividends Dividends Amount of gain (loss) recognized in other comprehensive income (loss) Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax Less: amount of (loss) gain reclassified in interest expense Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax Total change in other comprehensive income (loss) for unrealized gains (losses) on derivatives, before income tax benefit Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax Cash Flow Hedges Fair Value Hedges Notional values Derivative, Notional Amount Recorded Investment Impaired Financing Receivable, Recorded Investment Unpaid Principal Balance Impaired Financing Receivable, Unpaid Principal Balance Allowance Impaired Financing Receivable, Related Allowance Earnings Per Share [Abstract] Earnings per Common Share Earnings Per Share [Text Block] Accounting Policies [Abstract] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Consolidation Consolidation, Policy [Policy Text Block] Allowance for Loan Losses Loans and Leases Receivable, Allowance for Loan Losses Policy [Policy Text Block] Troubled Debt Restructurings Loans and Leases Receivable, Troubled Debt Restructuring Policy [Policy Text Block] Derivative Accounting Derivatives, Policy [Policy Text Block] Stock-Based Compensation Compensation Related Costs, Policy [Policy Text Block] Deposits - interest bearing Interest-bearing Deposit Liabilities Deposits - non-interest bearing Noninterest-bearing Deposit Liabilities Total deposits Deposits Numerator: Numerator [Abstract] Numerator. Net income Net Income (Loss) Attributable to Parent Preferred stock dividends Preferred Stock Dividends, Income Statement Impact Net income attributable to SLM Corporation common stock Net Income (Loss) Available to Common Stockholders, Basic Denominator: Denominator [Abstract] Denominator [Abstract] Weighted average shares used to compute basic EPS (in shares) Weighted Average Number of Shares Outstanding, Basic Effect of dilutive securities: Dilutive Securities, Effect on Basic Earnings Per Share [Abstract] Dilutive effect of stock options, restricted stock and restricted stock units and Employee Stock Purchase Plan (ESPP) (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Weighted average shares used to compute diluted EPS (in shares) Weighted Average Number of Shares Outstanding, Diluted Basic earnings per common share attributable to SLM Corporation (in dollars per share) Earnings Per Share, Basic Diluted earnings per common share attributable to SLM Corporation (in dollars per share) Earnings Per Share, Diluted Securities excluded from computation of EPS (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Income Statement [Abstract] Interest income: Investment Income, Interest and Dividend [Abstract] Loans Interest and Fee Income, Loans and Leases Investments Interest and Dividend Income, Securities, Operating, Available-for-sale Cash and cash equivalents Cash And Investments Interest Income Loss Cash and investments interest income (loss). Total interest income Interest and Dividend Income, Operating Interest expense: Interest Expense [Abstract] Deposits Interest Expense, Deposits Interest expense on short-term borrowings Interest Expense, Short-term Borrowings Interest expense on long-term borrowings Interest Expense, Long-term Debt Other interest expense Interest Expense, Other Total interest expense Interest Expense Net interest income Interest Income (Expense), Net Less: provisions for credit losses Provision for Loan, Lease, and Other Losses Net interest income after provisions for credit losses Interest Income (Expense), after Provision for Loan Loss Non-interest income: Noninterest Income [Abstract] Losses on derivatives and hedging activities, net Gain (Loss) on Derivative Instruments, Net, Pretax Other income Noninterest Income, Other Operating Income Total non-interest income Noninterest Income Non-interest expenses: Operating Expenses [Abstract] Compensation and benefits Labor and Related Expense FDIC assessment fees Federal Deposit Insurance Corporation Premium Expense Other operating expenses Other Noninterest Expense Total operating expenses Operating Expenses Acquired intangible asset amortization expense Acquired Intangible Assets Impairment And Amortization Expense Acquired intangible assets impairment and amortization expense. Total non-interest expenses Noninterest Expense Income before income tax expense Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Income tax expense Income Tax Expense (Benefit) Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Average common shares outstanding (in shares) Average common and common equivalent shares outstanding (in shares) Allowance for Loan Losses Allowance for Credit Losses [Text Block] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Private Education Loan securitization Private Education Loan Securitization [Member] Private Education Loan Securitization [Member] ABCP borrowings ABCP Borrowings [Member] ABCP Borrowings [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Short Term Short-term Debt Long Term Long-term Debt Total Debt, Long-term and Short-term, Combined Amount Schedule of compliance with regulatory capital requirements under banking regulations Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block] Document And Entity Information [Abstract] Document and Entity Information [Abstract] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Trading Symbol Trading Symbol Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding (in shares) Entity Common Stock, Shares Outstanding Loans in-school/grace/deferment Loans in forbearance Loans in repayment and percentage of each status: Loans current Private Education Loans deferred origination costs Net Unamortized Premium Or Discount Net unamortized premium or discount on loans receivable. Total Private Education Loans Loans Total loans. Private Education Loans allowance for losses Loans and Leases Receivable, Allowance Private Education Loans, net Loans Receivable, Net Percentage of Private Education Loans in repayment Percentage Of Loans In Repayment Percentage of loans in repayment. Delinquencies as a percentage of Private Education Loans in repayment Delinquencies As Percentage Of Loans In Repayment Delinquencies as a percentage of loans in repayment. Loans in forbearance as a percentage of Private Education Loans in repayment and forbearance Loans In Forbearance As Percentage Of Loans In Repayment And Forbearance Loans in forbearance as a percentage of loans in repayment and forbearance. Borrowings Debt Disclosure [Text Block] Average Balance, Private Education Loans Average balance of Private Education Loans Average balance of Private Education Loans Average Balance FFELP Loans Average Balance Ffelp Loans Average Balance Ffelp Loans Average Balance of Personal Loans Average Balance of Personal Loans Average Balance of Personal Loans Average Balance of Other Loans Average Balance of Other Loans Average Balance of Other Loans Average balance, Total portfolio Loans and Lease Receivable, Net, Average Balance Loans and Lease Receivable, Net, Average Balance Weighted Average Interest Rate, Other Loans Weighted Average Interest Rate, Other Loans Weighted Average Interest Rate, Other Loans Weighted Average Interest Rate, Private Education Loans Weighted Average Interest Rate of Private Education Loans Weighted Average Interest Rate FFELP loans Weighted Average Interest Rate Ffelp loans Weighted Average Interest Rate of Personal Loans Weighted Average Interest Rate of Personal Loans Weighted Average Interest Rate of Personal Loans Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Derivative [Table] Derivative [Table] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other Liabilities Other Liabilities [Member] Derivative [Line Items] Derivative [Line Items] Other Assets Derivative Asset [Abstract] Gross position Impact of master netting agreement Derivative Asset, Fair Value, Gross Liability Derivative values with impact of master netting agreements (as carried on balance sheet) Derivative Asset Cash collateral (held) pledged Derivative, Collateral, Obligation to Return Cash Net position Derivative Asset, Fair Value, Amount Offset Against Collateral Other Liabilities Derivative Liability [Abstract] Gross position Impact of master netting agreement Derivative Liability, Fair Value, Gross Asset Derivative values with impact of master netting agreements (as carried on balance sheet) Derivative Liability Cash collateral (held) pledged Derivative, Collateral, Right to Reclaim Cash Net position Derivative Liability, Fair Value, Amount Offset Against Collateral Industry of Counterparty, Type [Axis] Industry of Counterparty, Type [Axis] Industry of Counterparty [Domain] Industry of Counterparty [Domain] FFELP Loans Ffelp Loans [Member] FFELP loans. Private Education Loans Private Education Loans [Member] Private education loans. Personal Loans Personal Loans [Member] Personal Loans [Member] Allowance for Loan Losses Allowance For Credit Losses [Abstract] Allowance for credit losses. Allowance at beginning of period Total provision Provision for Loan and Lease Losses Net charge-offs: Allowance for Loan and Lease Losses Write-offs, Net [Abstract] Charge-offs Allowance for Loan and Lease Losses, Write-offs Recoveries Allowance for Loan and Lease Loss, Recovery of Bad Debts Net charge-offs Allowance for Loan and Lease Losses Write-offs, Net Loan sales Allowance for Loan and Lease Losses, Loans Sold Allowance at end of period Allowance: Allowance [Abstract] Allowance. Ending balance: individually evaluated for impairment Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment Ending balance: collectively evaluated for impairment Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment Loans: Loans [Abstract] Loans. Ending balance: individually evaluated for impairment Financing Receivable, Individually Evaluated for Impairment Ending balance: collectively evaluated for impairment Financing Receivable, Collectively Evaluated for Impairment Net charge-offs as a percentage of average loans in repayment (annualized) Charge Offs As Percentage Of Average Loans In Repayment Charge offs as percentage of average loans in repayment. Allowance as a percentage of the ending total loan balance Allowance As Percentage Of Ending Loan Balance Allowance as a percentage of the ending total loan balance. Allowance as a percentage of the ending loans in repayment Allowance As Percentage Of Ending Loans In Repayment Allowance as a percentage of the ending loans in repayment. Allowance coverage of net charge-offs (annualized) Annualized Allowance On Private Education Loan Coverage Of Charge Offs Annualized allowance on private education loan coverage of charge offs. Ending total loans, gross Allowance Coverage Of Charge Offs Ending Loans Allowance coverage of charge-offs ending total loans. Average loans in repayment Allowance Coverage Of Charge Offs Average Loans In Repayment Allowance coverage of charge offs average loans in repayment. Ending loans in repayment Allowance Coverage Of Charge Offs Ending Loans In Repayment Allowance coverage of charge-offs Ending loans in repayment. Shares repurchased related to employee stock-based compensation plans (in shares) Stock Repurchased During Period, Shares Average purchase price per share (in dollars per share) Treasury Stock Acquired, Average Cost Per Share Common shares issued (in shares) Stock Issued During Period, Shares, New Issues Loans Held for Investment Loans, Notes, Trade and Other Receivables Disclosure [Text Block] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Preferred Stock Preferred Stock [Member] Treasury Stock Treasury Stock [Member] Additional Paid-In Capital Additional Paid-in Capital [Member] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Retained Earnings Retained Earnings [Member] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning Balance (in shares) Shares, Outstanding Beginning Balance, shares issued (in shares) Shares, Issued Beginning Balance Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Net income Other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax Total comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Cumulative effect of the new stock compensation standard Cumulative Effect of Adoption of New Stock Compensation Amendment Cumulative Effect of Adoption of New Stock Compensation Amendment Cash dividends: Dividends, Cash [Abstract] Cash dividends, preferred stock Dividends, Preferred Stock, Cash Dividend equivalent units related to employee stock-based compensation plans Dividends, Share-based Compensation Issuance of common shares (in shares) Issuance of common shares Stock Issued During Period, Value, New Issues Tax benefit related to employee stock-based compensation Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net Stock-based compensation expense Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Shares repurchased related to employee stock-based compensation plans (in shares) Shares Paid for Tax Withholding for Share Based Compensation Shares repurchased related to employee stock-based compensation plans Adjustments Related to Tax Withholding for Share-based Compensation Ending Balance (in shares) Ending Balance, shares issued (in shares) Ending Balance Commitments and Contingencies Disclosure [Abstract] Commitments, Contingencies and Guarantees Commitments and Contingencies Disclosure [Text Block] Related Party Transactions [Abstract] Deferred taxes to be indemnified Deferred Tax Liabilities, Net Amount remaining Deferred Tax Assets, Amount Remaining Deferred Tax Assets, Amount Remaining Remaining balance of indemnification receivable in connection with the spin-off Deferred Tax Assets, Remaining Balance of Indemnification Receivable In Connection with The Spin-Off Deferred Tax Assets, Remaining Balance of Indemnification Receivable In Connection with The Spin-Off Liability for uncertainty in income taxes Liability for Uncertainty in Income Taxes, Current Liability for uncertainty in income taxes relating to historical transactions Liability for Uncertainty in Income Taxes, Noncurrent Actual Capital [Abstract] Common Equity Tier I Capital (to Risk-Weighted Assets) common equity tier 1 capital common equity tier 1 capital Tier 1 Capital (to Risk-Weighted Assets) Tier One Risk Based Capital Total Capital (to Risk-Weighted Assets) Capital Tier 1 Capital (to Average Assets) Tier One Leverage Capital Actual Ratio Risk Based Ratios [Abstract] Common Equity Tier I Capital (to Risk-Weighted Assets) Common Equity Tier 1 to Risk Weighted Assets Common Equity Tier 1 to Risk Weighted Assets Tier 1 Capital (to Risk-Weighted Assets) Tier One Risk Based Capital to Risk Weighted Assets Total Capital (to Risk-Weighted Assets) Capital to Risk Weighted Assets Tier 1 Capital (to Average Assets) Tier One Leverage Capital to Average Assets Well Capitalized Regulatory Requirements, Amount Tier One Leverage Capital [Abstract] Common Equity Tier I Capital (to Risk-Weighted Assets) common equity capital required to be well capitalized common equity capital required to be well capitalized Tier 1 Capital (to Risk-Weighted Assets) Tier One Risk Based Capital Required to be Well Capitalized Total Capital (to Risk-Weighted Assets) Capital Required to be Well Capitalized Tier 1 Capital (to Average Assets) Tier One Leverage Capital Required to be Well Capitalized Well Capitalized Regulatory Requirements, Ratio Leverage Ratios [Abstract] Common Equity Tier I Capital (to Risk-Weighted Assets) Common Equity Capital Required to Be Well Capitalized Percent Common Equity Capital Required to Be Well Capitalized Percent Tier 1 Capital (to Risk-Weighted Assets) Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets Total Capital (to Risk-Weighted Assets) Capital Required to be Well Capitalized to Risk Weighted Assets Tier 1 Capital (to Average Assets) Tier One Leverage Capital Required to be Well Capitalized to Average Assets Collateral [Axis] Collateral [Axis] Collateral [Domain] Collateral [Domain] 1-12 payments Seasoning Based On Monthly Scheduled Payments Due From One To Twelve Payments [Member] Seasoning Based On Monthly Scheduled Payments Due From One To Twelve Payments [Member] 13-24 payments Seasoning Based On Monthly Scheduled Payments Due From Thirteen To Twenty Four Payments [Member] Seasoning Based On Monthly Scheduled Payments Due From Thirteen To Twenty Four Payments [Member] 25-36 payments Seasoning Based On Monthly Scheduled Payments Due From Twenty Five To Thirty Six Payments [Member] Seasoning Based On Monthly Scheduled Payments Due From Twenty Five To Thirty Six Payments [Member] 37-48 payments Seasoning Based On Monthly Scheduled Payments Due From Thirty Seven To Forty Eight Payments [Member] Seasoning Based On Monthly Scheduled Payments Due From Thirty Seven To Forty Eight Payments [Member] More than 48 payments Seasoning Based On Monthly Scheduled Payments Due From More Than Forty Eight Payments [Member] Seasoning Based On Monthly Scheduled Payments Due From More Than Forty Eight Payments [Member] Not yet in repayment Seasoning Based On Monthly Scheduled Payments Due From Not Yet In Repayment [Member] Seasoning Based On Monthly Scheduled Payments Due From Not Yet In Repayment [Member] Credit Score, FICO [Axis] Credit Score, FICO [Axis] Credit Score, FICO [Domain] Credit Score, FICO [Domain] FICO score less than 670 FICO score less than 670 [Member] FICO score less than 670 [Member] FICO score 670-699 FICO score 670-699 [Member] FICO score 670-699 [Member] FICO score 700-749 FICO score 700-749 [Member] FICO score 700-749 [Member] FICO score greater than or equal to 750 FICO score greater than 750 [Member] FICO score greater than 750 [Member] Credit Quality Indicators [Axis] Credit Quality Indicators [Axis] Credit Quality Indicators [Axis] Credit Quality Indicators [Domain] Credit Quality Indicators [Domain] Credit Quality Indicators [Domain] With Cosigner With Cosigner [Member] With Cosigner [Member] Without Cosigner Without Cosigner [Member] Without Cosigner [Member] Cosigners Cosigner [Member] Cosigner credit quality indicators that are developed and used internally by the company. School Type/FICO Scores School Fico [Member] School type fico credit quality indicators that are developed and used internally by the company. Seasoning Repayments [Member] Repayments credit quality indicators that are developed and used internally by the company. Private Education Loans Private Education Loans Gross Private education loans gross. Private Education Loans with cosigner (in percentage) Percent Of Private Loans With Cosigner Percent of private loans with cosigner. Private Education Loans without cosigner (in percentage) Percent Of Private Loans Without Cosigner Percent of private loans without cosigner. Private Education Loans At Origination Private Education Loans At Origination Private Education Loans At Origination Total in percent Private Education Loans Gross In Percent Private education loans gross in percent. Seasoning based on monthly scheduled payments due from 1-12 payments (in percentage) Seasoning Based On Monthly Scheduled Payments Due From One To Twelve Payments In Percent Seasoning based on monthly scheduled payments due from one to twelve payments in percent. Seasoning based on monthly scheduled payments due from 13 - 24 payments (in percentage) Seasoning Based On Monthly Scheduled Payments Due From Thirteen To Twenty Four Payments In Percent Seasoning based on monthly scheduled payments due from thirteen to twenty four payments in percent. Seasoning based on monthly scheduled payments due from 25 - 36 payments (in percentage) Seasoning Based On Monthly Scheduled Payments Due From Twenty Five To Thirty Six Payments In Percent Seasoning based on monthly scheduled payments due from thirteen to twenty four payments in percent Seasoning based on monthly scheduled payments due from 37 - 48 payments (in percentage) Seasoning Based On Monthly Scheduled Payments Due From Thirty Seven To Forty Eight Payments In Percent Seasoning based on monthly scheduled payments due from thirty seven to forty eight payments in percent. Seasoning based on monthly scheduled payments due from more than 48 payments (in percentage) Seasoning Based On Monthly Scheduled Payments Due From More Than Forty Eight Payments In Percent Seasoning based on monthly scheduled payments due from more than forty eight payments in percent Seasoning based on monthly scheduled payments due from not yet in repayment (in percentage) Seasoning Based On Monthly Scheduled Payments Due From Not Yet In Repayment In Percent Seasoning based on monthly scheduled payments due from not yet in repayment in percent Subsequent Events [Abstract] Subsequent Event [Table] Subsequent Event [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Senior Notes Senior Notes [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Senior Unsecured Notes Due April 2022 Senior Unsecured Notes Due April 5, 2022 [Member] Senior Unsecured Notes Due April 5, 2022 [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Unsecured offering issued Interest rate stated percentage Debt Instrument, Interest Rate, Stated Percentage Redemption price percentage Preferred Stock, Dividend Rate, Percentage Modified Loans Modified Loans Modified Loans Charge-offs Charge Offs In TDR Portfolio Charge Offs In TDR Portfolio Payment- Default Troubled Debt Restructurings Payment Default Troubled Debt Restructurings Payment Default Deposits Deposit Liabilities Disclosures [Text Block] Significant Accounting Policies Significant Accounting Policies [Text Block] Derivative Financial Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Line of Credit Facility [Table] Line of Credit Facility [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Class A Notes Class A Notes [Member] Class A Notes [Member] Class A and B Notes Class A and B Notes [Member] Class A and B Notes [Member] Private Education Loans, 2016 Term A Private Education Loans, 2016 Term A [Member] Private Education Loans, 2016 Term A [Member] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Commercial Paper Commercial Paper [Member] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Private asset backed commercial paper education loan funding facility Line of Credit Facility, Maximum Borrowing Capacity Ownership interest percentage in residual interest in ABCP facility Ownership Interest Percentage Ownership Interest Percentage Financing cost percentage of unused borrowing capacity Debt Instrument, Unused Borrowing Capacity Fee, Percentage Debt Instrument, Unused Borrowing Capacity Fee, Percentage Basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Short-term borrowings Total loan amount securitized at inception Principal Amount Outstanding on Loans Held-for-sale or Securitization or Asset-backed Financing Arrangement Amount of loan securitization sold to third parties Continuing Involvement with Transferred Financial Assets, Principal Amount Outstanding Ownership interest percentage Loans Securitized or Asset-Backed Financing Arrangement, Ownership Interest, Percentage Loans Securitized or Asset-Backed Financing Arrangement, Ownership Interest, Percentage Proceeds from loan securitization sold to third parties Proceeds from Issuance of Unsecured Debt Loans pledged as collateral Loans Pledged as Collateral Uncommitted federal funds Uncommitted Federal Funds Uncommitted Federal Funds Lendable value of collateral Lendable value of collateral Lendable value of collateral Amount Interest-bearing Deposit Liabilities, Domestic, by Component [Abstract] Money market Interest-bearing Domestic Deposit, Money Market Savings Interest-bearing Domestic Deposit, Savings Certificates of deposit Interest-bearing Domestic Deposit, Time Deposits Deposits - interest bearing Weighted Average Stated Rate Weighted Average Rate Domestic Deposit Liabilities [Abstract] Money market Weighted Average Rate Domestic Deposit, Money Market Savings Weighted Average Rate Domestic Deposit, Savings Certificates of deposit Weighted Average Rate Domestic Deposit, Time Deposits Loss Contingencies [Table] Loss Contingencies [Table] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Contractual obligation Contractual Obligation Other liabilities reserve Other Liabilities Reserve Other Liabilities Reserve Loss contingency, loss emergence period Loss Contingency, Loss Emergence Period Loss Contingency, Loss Emergence Period Number of attorneys general Number of Attorneys General Number of Attorneys General Average Recorded Investment Impaired Financing Receivable, Average Recorded Investment Interest Income Recognized Impaired Financing Receivable, Interest Income, Cash Basis Method Period of forbearance within twenty-four month period to be classified as TDR (more than) Loans and Leases Receivable, Period of Forbearance Within Twenty-Four Month Period to be Classified as TDR Loans and Leases Receivable, Period of Forbearance Within Twenty-Four Month Period to be Classified as TDR Period after grace period for forbearance allowance Loans and Leases Receivable, Period After Grace Period for Forbearance Allowance Loans and Leases Receivable, Period After Grace Period for Forbearance Allowance Forbearance period after grace period Loans and Leases Receivable, Forbearance Period after Grace Period Loans and Leases Receivable, Forbearance Period after Grace Period Percentage of loans granted forbearance qualified as TDR Loans and Leases Receivable, Impaired, Loans Granted Forbearance Qualified as Trouble Debt Restructuring Loans and Leases Receivable, Impaired, Loans Granted Forbearance Qualified as Trouble Debt Restructuring Criteria for loans to be considered as nonperforming Criteria For Loans To Be Considered As Nonperforming Criteria for loans to be considered as nonperforming. Tier 1 of government guarantee (at least) (in percentage) TDR payment default period Payment Default Period For Troubled Debt Restructurings Payment Default Period For Troubled Debt Restructurings Period of loans past due that have accrued interest Period of Loans Past Due That Have Accrued Interest Period of Loans Past Due That Have Accrued Interest Loans held for investment Student Loan Portfolio By Program [Table Text Block] Student loan portfolio by program. Statement of Financial Position [Abstract] Amortized cost Available-for-sale Debt Securities, Amortized Cost Basis Allowance for loan losses Tax benefit for accumulated other comprehensive (loss) income AOCI Tax, Attributable to Parent Preferred stock, stated value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Preferred stock shares authorized (in shares) Preferred Stock, Shares Authorized Preferred stock shares outstanding (in shares) Preferred Stock, Shares Outstanding Common stock par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares authorized (in shares) Common Stock, Shares Authorized Common stock shares issued (in shares) Common Stock, Shares, Issued Common stock held in treasury (in shares) Treasury Stock, Shares Chicago Mercantile Exchange CHICAGO MERCANTILE EXCHANGE [Member] London Clearing House London Clearing House [Member] London Clearing House [Member] Contracts other than CME Contracts Other Than Chicago Mercantile Exchange [Member] Contracts Other Than Chicago Mercantile Exchange [Member] Notional value Derivative instruments Increase (decrease) in fair value of collateral Derivative Liability, Increase (Decrease) in Fair Value of Collateral Derivative Liability, Increase (Decrease) in Fair Value of Collateral Variation margin Net position Cash collateral (held) pledged Percent of total notional derivative contracts Derivative Instrument, Percent of Total Notional Derivative Contracts Derivative Instrument, Percent of Total Notional Derivative Contracts Net derivatives Derivative Assets (Liabilities), at Fair Value, Net Cash collateral held relative to derivative exposure Derivative, Cash Collateral Held Relative to Derivative Exposure, Net Derivative, Cash Collateral Held Relative to Derivative Exposure, Net Cash collateral pledged Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Fair Value Hedges Gain (Loss) on Fair Value Hedges Recognized in Earnings [Abstract] Hedge ineffectiveness gains (losses) recorded in earnings Gain (Loss) on Fair Value Hedge Ineffectiveness, Net Realized gains recorded in interest expense Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net Cash Flow Hedges Effect of Cash Flow Hedges on Results of Operations [Abstract] Hedge ineffectiveness losses recorded in earnings Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net Realized losses recorded in interest expense Gain (Loss) from Components Excluded from Assessment of Cash Flow Hedge Effectiveness, Net Trading Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract] Interest reclassification Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net, Interest Reclassification Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net, Interest Reclassification Realized (losses) gains recorded in earnings Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net, Hedge Ineffectiveness Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net, Hedge Ineffectiveness Gain (loss) on derivatives, net Derivative, Gain (Loss) on Derivative, Net Deferred origination costs Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums Allowance for loan losses Allowance For Private Education Loans Losses Allowance for private education loans losses. Total Private Education Loans, net Private Education Loans Net Private education loans net. FFELP Loans Ffelp Loans FFELP loans. Unamortized acquisition costs, net Ffelp origination fees, net Ffelp origination fees, net Allowance for loan losses Ffelp Loan Allowance For Losses FFELP loan allowance for losses. Total FFELP Loans, net Ffelp Loans Net FFELP loans, net. Personal Loans Loans and Leases Receivable, Personal Loans Loans and Leases Receivable, Personal Loans Allowance for loan losses Loans and Leases Receivable, Allowance for Loan Losses Loans and Leases Receivable, Allowance for Loan Losses Total Personal Loans, net Loans and Leases Receivable, Personal Loans, Total Loans and Leases Receivable, Personal Loans, Total Loans held for investment, net Loans and Leases Receivable, Net Amount Schedule of earnings per share, basic and diluted Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of Error Corrections and Prior Period Adjustment Restatement [Table] Schedule of Error Corrections and Prior Period Adjustment Restatement [Table] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Accounting Standards Update 2016-09 Accounting Standards Update 2016-09 [Member] Accounting Standards Update 2016-09 [Member] New Accounting Pronouncement, Early Adoption [Axis] New Accounting Pronouncement, Early Adoption [Axis] New Accounting Principles, Early Adoption [Domain] New Accounting Principles, Early Adoption [Domain] New Accounting Pronouncement, Early Adoption, Effect New Accounting Pronouncement, Early Adoption, Effect [Member] Error Corrections and Prior Period Adjustments Restatement [Line Items] Error Corrections and Prior Period Adjustments Restatement [Line Items] Benefit in income tax expense due to new standard Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount Cumulative effect adjustment to retained earnings Cumulative Effect of New Accounting Principle in Period of Adoption Statement of Comprehensive Income [Abstract] Net income Other comprehensive income (loss): Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract] Unrealized (losses) gains on investments Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax Unrealized gains (losses) on cash flow hedges Total unrealized gains (losses) Other Comprehensive Income (Loss), before Tax Income tax (expense) benefit Other Comprehensive Income (Loss), Tax Other comprehensive income (loss), net of tax (expense) benefit Total comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Subsequent Event Subsequent Events [Text Block] Stable interest-bearing deposits, total Stable Interest-bearing Deposits, Total Stable Interest-bearing Deposits, Total Brokered deposit placement fee Brokered Deposit Placement Fee Brokered Deposit Placement Fee Third party broker fees paid Third Party Broker Fees Paid Third Party Broker Fees Paid Deposits exceeding FDIC insurance limits Time Deposits, $100,000 or More Accrued interest on deposits Interest Payable, Current Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement [Member] Portion at Fair Value Measurement [Member] Fair Value Estimate of Fair Value Measurement [Member] Carrying Value Reported Value Measurement [Member] Liability Class [Axis] Liability Class [Axis] Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Money-market and savings accounts Money Market and Savings Accounts [Member] Money Market and Savings Accounts [Member] Certificates of deposit Certificates of Deposit [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Earning assets Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] Loans held for investment, net Loans Receivable, Fair Value Disclosure Loans held for investment, net, difference Loans Receivable, Fair Value Disclosure, Difference Between Carrying Value and Fair Value Loans Receivable, Fair Value Disclosure, Difference Cash and cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Available-for-sale investments Investments, Fair Value Disclosure Accrued interest receivable Accrued Interest Receivable, Fair Value Disclosure Accrued Interest Receivable, Fair Value Disclosure Tax indemnification receivable Income Taxes Receivable Derivative instruments Total earning assets Assets, Fair Value Disclosure Total earning assets, difference Assets, Fair Value Disclosure, Difference Between Carrying Value and Fair Value Assets, Fair Value Disclosure, Difference Between Carrying Value and Fair Value Interest-bearing liabilities Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Deposits Deposits, Fair Value Disclosure Certificates of deposit, difference Deposits, Fair Value Disclosure, Difference Between Carrying Value and Fair Value Deposits, Fair Value Disclosure, Difference Between Carrying Value and Fair Value Short-term borrowings Short-term Debt, Fair Value Long-term borrowings Long-term Debt, Fair Value Long-term borrowings, difference Long-term Debt, Fair Value, Difference Between Carrying Value and Fair Value Long-term Debt, Fair Value, Difference Between Carrying Value and Fair Value Accrued interest payable Accrued Liabilities, Fair Value Disclosure Total interest-bearing liabilities Financial Liabilities Fair Value Disclosure Total interest-bearing liabilities, difference Financial Liabilities Fair Value Disclosure, Difference Between Carrying Value and Fair Value Financial Liabilities Fair Value Disclosure, Difference Between Carrying Value and Fair Value Excess of net asset fair value over carrying value Excess Of Net Asset Fair Value Over Carrying Value Excess of net asset fair value over carrying value. Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Fair Value Measurements Recurring Fair Value, Measurements, Recurring [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Level 1 Fair Value, Inputs, Level 1 [Member] Level 2 Fair Value, Inputs, Level 2 [Member] Level 3 Fair Value, Inputs, Level 3 [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Assets Assets, Fair Value Disclosure [Abstract] Available-for-sale investments Available-for-sale Securities, Debt Securities Liabilities Liabilities, Fair Value Disclosure [Abstract] Derivative instruments Variable Interest Entities [Axis] Variable Interest Entities [Axis] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Primary Beneficiary Variable Interest Entity, Primary Beneficiary [Member] ABCP Facility Debt Outstanding Debt, Long-term and Short-term, Combined Amount [Abstract] Carrying Amount of Assets Securing Debt Outstanding Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract] Loans Carrying Amount Of Assets Securing Debt Outstanding Loans Carrying Amount Of Assets Securing Debt Outstanding Loans Restricted Cash Restricted Cash and Investments Other Assets Other Assets Total Variable Interest Entity, Consolidated, Carrying Amount, Assets Assets Assets [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Available-for-sale investments at fair value (cost of $221,265 and $211,406, respectively) Loans held for investment (net of allowance for losses of $187,086 and $184,701, respectively) Restricted cash and investments Other interest-earning assets Other Interest Earning Assets Accrued interest receivable Interest Receivable Premises and equipment, net Property, Plant and Equipment, Net Other assets Total assets Assets Liabilities Liabilities [Abstract] Deposits Long-term borrowings Income taxes payable, net Taxes Payable Upromise member accounts Upromise related liability Upromise related liability Other liabilities Other Liabilities Total liabilities Liabilities Commitments and contingencies Commitments and Contingencies Equity Stockholders' Equity Attributable to Parent [Abstract] Preferred stock value outstanding Preferred Stock, Value, Outstanding Common stock, par value $0.20 per share, 1.125 billion shares authorized: 440.4 million and 436.6 million shares issued, respectively Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital Accumulated other comprehensive loss (net of tax benefit of $4,132 and $5,364, respectively) Accumulated Other Comprehensive Income (Loss), Net of Tax Retained earnings Retained Earnings (Accumulated Deficit) Total SLM Corporation stockholders’ equity before treasury stock Stockholders' Equity Attributable to Parent, Excluding Treasury Stock Stockholders' Equity Attributable to Parent, Excluding Treasury Stock Less: Common stock held in treasury at cost: 9.3 million and 7.7 million shares, respectively Treasury Stock, Value Total equity Total liabilities and equity Liabilities and Equity Impact of derivatives on the consolidated balance sheet Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Offsetting assets Offsetting Assets [Table Text Block] Offsetting liabilities Offsetting Liabilities [Table Text Block] Schedule of notional amounts of outstanding derivative positions Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] Derivative instruments, gain (loss) Derivative Instruments, Gain (Loss) [Table Text Block] Schedule of derivative instruments, effect on other comprehensive income (loss) Schedule of Derivative Instruments, Effect on Other Comprehensive Income (Loss) [Table Text Block] Arrangements with Navient Corporation Related Party Transactions Disclosure [Text Block] Statement of Cash Flows [Abstract] Operating activities Net Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash used in operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Provisions for credit losses Provision for Doubtful Accounts Income tax expense Deferred Income Tax Expense (Benefit) Amortization of brokered deposit placement fee Amortization of Brokered Deposit Placement amortization of brokered deposit placement Amortization of ABCP Facility upfront fee Amortization of Upfront Loan Fees Amortization of Upfront Loan Fees Amortization of deferred loan origination costs and fees, net Amortization of Deferred Loan Origination Fees, Net Net amortization of discount on investments Accretion (Amortization) of Discounts and Premiums, Investments Interest income on tax indemnification receivable Interest Income on Tax Indemnification Receivable Interest Income on Tax Indemnification Receivable Depreciation of premises and equipment Depreciation Amortization of acquired intangibles Amortization of Intangible Assets Stock-based compensation expense Share-based Compensation Unrealized losses on derivative and hedging activities, net Unrealized Gain (Loss) on Derivatives Other adjustments to net income, net Other Noncash Income (Expense) Changes in operating assets and liabilities: Increase (Decrease) in Operating Assets [Abstract] Increase in accrued interest receivable Increase (Decrease) in Accrued Interest Receivable, Net Decrease in restricted cash and investments, net Increase (Decrease) in Restricted Cash Increase in other interest-earning assets Payments for (Proceeds from) Other Interest Earning Assets Increase in other assets Increase (Decrease) in Other Operating Assets Decrease in income taxes payable, net Increase (Decrease) in Income Taxes Payable Increase in accrued interest payable Increase (Decrease) in Interest Payable, Net Increase in payable due to entity that is a subsidiary of Navient Increase (Decrease) in Due to Related Parties (Decrease) increase in other liabilities Increase (Decrease) in Other Operating Liabilities Total adjustments Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities Total net cash used in operating activities Net Cash Provided by (Used in) Operating Activities Investing activities Net Cash Provided by (Used in) Investing Activities [Abstract] Loans acquired and originated Student Loans acquired and originated Student Loans acquired and originated Net proceeds from sales of loans held for investment Net proceeds from sales of student loans held for investment Net proceeds from sales of student loans held for investment Proceeds from claim payments Proceeds from Claim payments Proceeds from Claim payments Net decrease in loans held for investment Net (increase) decrease in loans held for investment Net (increase) decrease in loans held for investment Increase in restricted cash and investments - variable interest entities Increase (Decrease) in Restricted Cash and Investments Purchases of available-for-sale securities Payments to Acquire Available-for-sale Securities Proceeds from sales and maturities of available-for-sale securities Proceeds from Sale and Maturity of Available-for-sale Securities Total net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Financing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Brokered deposit placement fee Cash paid for brokered deposit placement fee Cash paid for brokered deposit placement fee Net decrease in certificates of deposit Net increase (decrease) in brokered certificates of deposit Net increase (decrease) in brokered certificates of deposit Net increase in other deposits Net increase in NOW account deposits Net increase in NOW account deposits Borrowings collateralized by loans in securitization trusts - issued Borrowings Collateralized By Loans In Trust Issued Borrowings Collateralized By Loans In Trust Issued Borrowings collateralized by loans in securitization trusts - repaid Borrowings Collateralized By Loans In Trust Repaid Borrowings Collateralized By Loans In Trust Repaid Issuance costs for collateralized borrowings Payments of Debt Issuance Costs Borrowings under ABCP Facility Proceeds from Issuance of Commercial Paper Fees paid on ABCP Facility Net Increase (Decrease) in Upfront Loan Fees Net Increase (Decrease) in Upfront Loan Fees Preferred stock dividends paid Payments of Dividends Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Net decrease in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period Cash disbursements made for: Supplemental Cash Flow Information [Abstract] Interest Interest Paid Income taxes paid Income Taxes Paid Income taxes refunded Proceeds from Income Tax Refunds Schedule of common share repurchases Class of Treasury Stock [Table Text Block]