Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Trading Arrangement: Trading Arrangement [Axis] Maximum Maximum [Member] Financing receivable, held-for-sale Financing Receivable, Held-for-Sale Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Short-Term Debt, Type [Axis] Short-Term Debt, Type [Axis] Title of 12(b) Security Title of 12(b) Security Carrying Value Reported Value Measurement [Member] Net income attributable to SLM Corporation common stock Net Income (Loss) Available to Common Stockholders, Diluted Financing receivable, held for sale, accrued interest Financing Receivable, Held For Sale, Accrued Interest Financing Receivable, Held For Sale, Accrued Interest Subsequent Event Subsequent Event [Member] Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-Sale [Table] 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] Total net derivatives Derivative Assets (Liabilities), at Fair Value, Net Net charge-offs: Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery [Abstract] Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) [Table] Net charge-offs Current period net charge-offs, total Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff (Recovery) Adjustment to Compensation, Amount Adjustment to Compensation Amount Total Capital (to Risk-Weighted Assets) Banking Regulation, Total Risk-Based Capital Ratio, Actual Financial Instrument [Axis] Financial Instrument [Axis] Segment Reporting [Abstract] Total provisions Financing Receivable, Allowance For Credit Loss, Excluding Accrued Interest, Period Increase (Decrease) Before Write-Off (Recovery) Financing Receivable, Allowance For Credit Loss, Excluding Accrued Interest, Period Increase (Decrease) Before Write-Off (Recovery) Weighted average life of loans Weighted Average Life of Loans Weighted Average Life of Loans Current period recoveries, After Year 5 Financing Receivable, Allowance for Credit Loss, Recovery, Originated Five Or More Years Before Current Fiscal Year Financing Receivable, Allowance for Credit Loss, Recovery, Originated Five Or More Years Before Current Fiscal Year 2054 Maturity 2054 [Member] Maturity 2054 Amortization of deferred loan origination costs and loan premium/(discounts), net Amortization of Deferred Loan Origination Fees, Net Derivative Instrument [Axis] Derivative Instrument [Axis] Measurement Frequency [Axis] Measurement Frequency [Axis] Industry of Counterparty, Type [Axis] Industry of Counterparty, Type [Axis] Allowance for Uncollectible Interest Allowance For Uncollectible Accrued Interest Allowance For Uncollectible Accrued Interest Consolidated Entities [Axis] Consolidated Entities [Axis] Average purchase price per share (in dollars per share) Shares Acquired, Average Cost Per Share Equity securities without readily determinable fair value, downward price adjustment, annual amount Equity Securities without Readily Determinable Fair Value, Downward Price Adjustment, Annual Amount Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Developed technologies Developed Technology Rights [Member] Borrowings collateralized by loans in securitization trusts - repaid Borrowings Collateralized By Loans In Trust Repaid Borrowings Collateralized By Loans In Trust Repaid Third party broker fees paid Third Party Broker Fees Paid Third Party Broker Fees Paid Current period net charge-offs, Year 1 Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery, Originated In Current Fiscal Year Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery, Originated In Current Fiscal Year Number of monthly payments required by a borrower between successive grants of forbearance Financing Receivable, Number Of Monthly Payments Required Between Forbearance Grants Financing Receivable, Number Of Monthly Payments Required Between Forbearance Grants Deposits Deposit Liabilities Disclosures [Text Block] Interest Rate Reduction Contractual Interest Rate Reduction [Member] Schedule of Compliance with Regulatory Capital Requirements Under Banking Regulations Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block] Tier 1 Capital (to Risk-Weighted Assets) Banking Regulation, Tier 1 Risk-Based Capital, Actual Consolidated Entities [Domain] Consolidated Entities [Domain] Gross Unrealized Losses Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss Less than 12 months Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract] After Year 5 Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Reclassification out of Accumulated Other Comprehensive Income Reclassification out of Accumulated Other Comprehensive Income [Member] Total Private Education Loans, Year 2 Loans, Originated In Fiscal Year Before Latest Fiscal Year Loans, Originated In Fiscal Year Before Latest Fiscal Year Net amortization of discount on investments Accretion (Amortization) of Discounts and Premiums, Investments Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Number of reportable segments Number of Reportable Segments Customer relationships Customer Relationships [Member] Net increase (decrease) in certificates of deposit Net Increase (Decrease) In Brokered Certificates Of Deposit Net Increase (Decrease) In Brokered Certificates Of Deposit Amortized Cost Basis Financing Receivable, Excluding Accrued Interest, Before Allowance For Credit Losses, Loan Modifications, Amortized Cost Financing Receivable, Excluding Accrued Interest, Before Allowance For Credit Losses, Loan Modifications, Amortized Cost Short-Term Debt, Type [Domain] Short-Term Debt, Type [Domain] Percentage of Private Education Loans in repayment, Year 2 Percentage Of Loans In Repayment, Originated In Fiscal Year Before Latest Fiscal Year Percentage Of Loans In Repayment, Originated In Fiscal Year Before Latest Fiscal Year Estimated accumulated gain (loss) to be reclassified in next 12 months Cash Flow Hedge Gain (Loss) to be Reclassified within 12 Months Entity Address, City or Town Entity Address, City or Town Accrued interest receivable, difference Accrued Interest Receivable, Fair Value Disclosure, Difference Accrued Interest Receivable, Fair Value Disclosure, Difference Class of Financing Receivable [Domain] Class of Financing Receivable [Domain] Receivables [Abstract] Receivables [Abstract] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Loans acquired and originated Student Loans Acquired And Originated Student Loans Acquired And Originated 2026-B ABS transaction SMB Private Education Loan Trust 2026-B term ABS [Member] SMB Private Education Loan Trust 2026-B term ABS Net Intangible Asset, Finite-Lived, after Accumulated Amortization Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Sallie.com domain Partner Relationships [Member] Partner Relationships Level 2  Fair Value, Inputs, Level 2 [Member] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Other comprehensive income (loss), net of tax (expense) benefit Other comprehensive loss, net of tax Other Comprehensive Income (Loss), Net of Tax Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Loan delinquent 90 days or greater past due Financial Asset, Equal to or Greater than 90 Days Past Due [Member] Other operating expenses Other Expenses 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 Subsequent Event Type [Axis] Subsequent Event Type [Axis] Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Schedule of Interest Bearing Deposits Interest Bearing Deposits [Table Text Block] [Table Text Block] for Interest Bearing Deposits [Table] Current period gross charge-offs, Year 4 Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Writeoff, Originated Three Years Before Latest Fiscal Year Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Writeoff, Originated Three Years Before Latest Fiscal Year Segment Reporting Segment Reporting [Table Text Block] Accrued interest to be capitalized Accrued Interest to be Capitalized [Abstract] Accrued Interest to be Capitalized Accelerated Share Repurchase Agreement Accelerated Share Repurchase Agreement [Member] Accelerated Share Repurchase Agreement Total accrued interest by origination vintage, Year 1 Financing Receivable, Accrued Interest, Origination Vintage, Originated in Current Fiscal Year Financing Receivable, Accrued Interest, Origination Vintage, Originated in Current Fiscal Year Loan sale reduction to provision Loan sale reduction to provision Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Loan Sold Seasoning based on monthly scheduled payments due from 37 - 48 payments 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. Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest Allowance for credit losses Allowance for loan losses, beginning balance Allowance for loan losses, ending balance Private Education Loans allowance for losses Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest Document Period End Date Document Period End Date Total Private Education Loans in Repayment, Year 4 Loans In Repayment, Originated Three Years Before Current Fiscal Year Loans In Repayment, Originated Three Years Before Current Fiscal Year Preferred stock, shares issued (in shares) Beginning balance, Preferred stock, shares issued (in shares) Ending balance, Preferred stock, shares issued (in shares) Preferred Stock, Shares Outstanding Notes Issued Debt Instrument, Face Amount Trading - Residual Interests Retained Interest [Member] Cash collateral pledged Derivative Asset, Subject To Master Netting Arrangement, Collateral, Obligation To Return Cash Not Offset Derivative Asset, Subject To Master Netting Arrangement, Collateral, Obligation To Return Cash Not Offset Less: Common stock held in treasury at cost: 257.7 million and 244.0 million shares, respectively Treasury Stock, Common, Value Trading Activity, by Type [Domain] Trading Activity, by Type [Domain] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income [Domain] Issuance of common shares (in shares) Stock Issued During Period, Shares, New Issues Including Dividend Equivalents Stock Issued During Period, Shares, New Issues Including Dividend Equivalents Criteria for loans to be considered as nonperforming (greater than) Criteria For Loans To Be Considered As Nonperforming Criteria for loans to be considered as nonperforming. Accumulated other comprehensive loss (net of tax benefit of ($14,669) and ($13,446), respectively) Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Shell Company Entity Shell Company Current period gross charge-offs, Year 3 Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Writeoff, Originated Two Years Before Latest Fiscal Year Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Writeoff, Originated Two Years Before Latest Fiscal Year Trade names and trademarks Trademarks and Trade Names [Member] 2046 Maturity 2046 [Member] Maturity 2046 [Member] Earnings per Common Share Earnings Per Share [Text Block] Earnings Per Share [Abstract] Earnings Per Share [Abstract] Document Fiscal Period Focus Document Fiscal Period Focus Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Seasoning based on monthly scheduled payments due from not yet in repayment 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 Equity Interests Debt Securities, Trading, and Equity Securities, FV-NI Total liabilities Liabilities Trading Symbol Trading Symbol Financing Receivable, Allowance for Credit Loss [Line Items] Financing Receivable, Allowance for Credit Loss [Line Items] Company Selected Measure Name Company Selected Measure Name Included in other comprehensive income Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) Purchases of available-for-sale securities Payments to Acquire Debt Securities, Available-for-Sale 2026-C ABS transaction SMB Private Education Loan Trust 2026-C term ABS [Member] SMB Private Education Loan Trust 2026-C term ABS Decrease in other interest-earning assets Payments for (Proceeds from) Other Interest Earning Assets Deposits Interest Expense, Deposits Seasoning Repayments [Member] Repayments credit quality indicators that are developed and used internally by the company. Unfunded loan held-for-sale Unfunded Loan Held-for-Sale Unfunded Loan Held-for-Sale Year 1 Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year Credit Facility [Domain] Credit Facility [Domain] Utah Housing Corporation bonds Utah Housing Corporation Bonds [Member] Utah Housing Corporation Bonds [Member] Operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Common stock dividend (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Loan principal Financing Receivable, Sale, Principal Financing Receivable, Sale, Principal Allowance for Credit Losses and Unfunded Loan Commitments Allowance for Credit Losses [Text Block] Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] 90 Days or Greater Past Due Greater Than Ninety Days Past Due Accrued Interest Receivable Greater than ninety days past due accrued interest receivable. Transfers out of level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 Line of Credit Facility [Table] Line of Credit Facility [Table] Dividends Dividends Tier 1 Capital (to Average Assets) Banking Regulation, Tier 1 Leverage Capital, Actual Common Equity Tier 1 Capital (to Risk-Weighted Assets) Tier One Risk Based Capital For Common Equity Required To Be Capitalized Tier One Risk Based Capital For Common Equity Required To Be Capitalized Senior Unsecured Notes Due January 31, 2030 Senior Unsecured Notes Due January 31, 2030 [Member] Senior Unsecured Notes Due January 31, 2030 Entities [Table] Entities [Table] Provisions for unfunded loan commitments Financing Receivable, Credit Loss, Expense (Reversal), Existing Commitments Financing Receivable, Credit Loss, Expense (Reversal), Existing Commitments Total Private Education Loans, Year 5 Loans, Originated Four Years Before Latest Fiscal Year Loans, Originated Four Years Before Latest Fiscal Year Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Rule 10b5-1 Trading Plan Rule 10b5-1 Trading Plan [Member] Rule 10b5-1 Trading Plan Award Timing Predetermined Award Timing Predetermined [Flag] Deposits, difference Deposits, Fair Value Disclosure, Difference Between Carrying Value And Fair Value Deposits, Fair Value Disclosure, Difference Between Carrying Value And Fair Value Current period recoveries, Year 2 Financing Receivable, Allowance for Credit Loss, Recovery, Originated In Fiscal Year Before Latest Fiscal Year Financing Receivable, Allowance for Credit Loss, Recovery, Originated In Fiscal Year Before Latest Fiscal Year Other comprehensive income: Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract] Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Stock-based compensation expense APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Level 1  Fair Value, Inputs, Level 1 [Member] Unfunded loan commitments sold Off-Balance Sheet, Credit Loss, Liability, Unfunded Loan Commitments Off-Balance Sheet, Credit Loss, Liability, Unfunded Loan Commitments Dilutive effect of stock options, restricted stock, restricted stock units, performance stock units, and Employee Stock Purchase Plan (“ESPP”) (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements 12 months or more Debt Securities, Available-for-Sale [Abstract] Hedged items recorded in interest expense Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge Common stock repurchased Stock Repurchased and Retired During Period, Value Class of Financing Receivable [Axis] Class of Financing Receivable [Axis] Private Education Loans allowance for losses, Year 1 Financing Receivable, Allowance For Credit Loss, Originated In Current Fiscal Year Financing Receivable, Allowance For Credit Loss, Originated In Current Fiscal Year Preferred stock, par or stated value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Long-term borrowings Long-Term Debt, Fair Value Depreciation of premises and equipment Depreciation 2026 Senior Notes 2026 Senior Notes [Member] 2026 Senior Notes Private education loans Percent Of Private Loans Percent of private loans Collateralized Securities Collateralized Securities [Member] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Derivatives recorded in interest expense Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments Investments Investment in Debt and Equity Securities and Other Trading Assets [Text Block] Common stock dividends paid Payments of Ordinary Dividends, Common Stock Private Education Loans, net, Year 3 Financing Receivable, after Allowance for Credit Loss, Originated Two Years Before Current Fiscal Year Financing Receivable, after Allowance for Credit Loss, Originated Two Years Before Current Fiscal Year Expiration Date Trading Arrangement Expiration Date Hedging Relationship [Axis] Hedging Relationship [Axis] Cash and cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Certificates of deposit Weighted Average Rate Domestic Deposit, Time Deposits Line of credit facility, expiration period Line of Credit Facility, Expiration Period Unsecured debt Unsecured Debt Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] 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 Measurement Input, Default Rate Measurement Input, Default Rate [Member] Derivative [Table] Derivative [Table] Weighted Average Interest Rate Weighted Average Interest Rate On Loans Weighted Average Interest Rate On Loans Deposits - interest-bearing Deposits - interest bearing Interest-Bearing Deposit Liabilities Loans transferred to held for sale Debt Securities, Available-for-Sale, Transfer out, Allowance for Credit Loss, Expense Reversal Other liabilities reserve Other Liabilities Reserve Other Liabilities Reserve Industry of Counterparty [Domain] Industry of Counterparty [Domain] Deposits Deposits, Fair Value Disclosure Investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Proceeds from sales and maturities of available-for-sale securities Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale Other Assets Derivative Asset [Abstract] CME CHICAGO MERCANTILE EXCHANGE [Member] Current period gross charge-offs, Year 2 Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Writeoff, Originated In Fiscal Year Before Latest Fiscal Year Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Writeoff, Originated In Fiscal Year Before Latest Fiscal Year Segments [Domain] Segments [Domain] Interest rate swaps Interest rate swaps Interest Rate Swap [Member] Total accrued interest by origination vintage Financing Receivable, Accrued Interest, Origination Vintage, before Allowance for Credit Loss Financing Receivable, Accrued Interest, Origination Vintage, before Allowance for Credit Loss Borrowings Debt Disclosure [Text Block] 2058 Maturity 2058 [Member] Maturity 2058 Contractual obligation Contractual Obligation PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Secured Borrowings Secured Debt [Member] Schedule of Accrued Interest Receivable Accrued Interest Receivable [Table Text Block] Accrued interest receivable. Loans held for sale Financing Receivable, Held-for-Sale, Not Part of Disposal Group, after Valuation Allowance Debt instrument, interest rate, stated percentage Debt Instrument, Interest Rate, Stated Percentage Common Stock Dividends, Common Stock, Cash Total equity Beginning balance Ending balance Equity, Attributable to Parent Financing receivable, modified in period, to total financing receivable, percentage Financing Receivable, Modified in Period, to Total Financing Receivables, Percentage Uncommitted federal funds Uncommitted Federal Funds Uncommitted Federal Funds Assets Assets [Abstract] Less: provisions for credit losses Provisions for credit losses Financing Receivable And Off-Balance Sheet, Excluding Accrued Interest, Credit Loss, Expense (Reversal) Financing Receivable And Off-Balance Sheet, Excluding Accrued Interest, Credit Loss, Expense (Reversal) Other investments Other Investments Available-for sale investments at fair value, cost Amortized Cost Debt Securities, Available-for-Sale, Amortized Cost Variable-rate Variable-rate Variable Income Interest Rate [Member] Schedule of Private Education Loan Portfolio Stratified by Key Credit Quality Indicators Financing Receivable Credit Quality Indicators [Table Text Block] Professional fees Professional Fees Insider Trading Policies and Procedures [Line Items] Amortization of brokered deposit placement fee Amortization Of Brokered Deposit Placement amortization of brokered deposit placement Private Education Loans, net, Year 2 Financing Receivable, after Allowance for Credit Loss, Originated In Fiscal Year Before Latest Fiscal Year Financing Receivable, after Allowance for Credit Loss, Originated In Fiscal Year Before Latest Fiscal Year Income taxes refunded Proceeds from Income Tax Refunds Income tax expense Deferred Income Tax Expense (Benefit) Financing Receivable Portfolio Segment [Domain] Financing Receivable Portfolio Segment [Domain] Interest income: Investment Income, Interest and Dividend [Abstract] Antidilutive securities excluded from computation of earnings per share (less than) (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Entity Central Index Key Entity Central Index Key Net interest income after provisions for credit losses Interest Income (Expense), after Provision for Loan Loss Equity [Abstract] Equity [Abstract] Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Greater than or equal to 750 FICO score greater than 750 [Member] FICO score greater than 750 [Member] Private Education Loans allowance for losses, After Year 5 Financing Receivable, Allowance For Credit Loss, Originated Five Years Before Current Fiscal Year Financing Receivable, Allowance For Credit Loss, Originated Five Years Before Current Fiscal Year Total Private Education Loans, gross, Year 2 Loans Gross, Originated In Fiscal Year Before Latest Fiscal Year Loans Gross, Originated In Fiscal Year Before Latest Fiscal Year Increase in non-marketable securities Increase (Decrease) in Equity Securities, FV-NI Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Preferred Stock Dividends, Preferred Stock, Cash Designated as Hedging Instrument Designated as Hedging Instrument [Member] Current period recoveries, Year 4 Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery, Originated Three Years Before Current Fiscal Year Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery, Originated Three Years Before Current Fiscal Year % of Balance Percent Of Balance [Abstract] Percent Of Balance Total Private Education Loans in forbearance, Year 1 Financing Receivable, Loans In Forbearance, Originated In Current Fiscal Year Financing Receivable, Loans In Forbearance, Originated In Current Fiscal Year Total Private Education Loans in Repayment, Year 2 Loans In Repayment, Originated In Fiscal Year Before Latest Fiscal Year Loans In Repayment, Originated In Fiscal Year Before Latest Fiscal Year Accumulated Other Comprehensive Loss AOCI Attributable to Parent [Member] Total Capital (to Risk-Weighted Assets) Banking Regulation, Total Risk-Based Capital Ratio, Well Capitalized, Minimum All Individuals All Individuals [Member] With cosigner With Cosigner [Member] With Cosigner [Member] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Combination - Interest Rate Reduction and Term Extension Interest Rate Reduction And Term Extension [Member] Interest Rate Reduction And Term Extension Delinquent Private Education Loans in repayment as a percentage of Private Education Loans in repayment, After Year 5 Delinquencies As Percentage Of Loans In Repayment, Originated Five Years Before Current Fiscal Year Delinquencies As Percentage Of Loans In Repayment, Originated Five Or More Years Before Current Fiscal Year Statement [Line Items] Statement [Line Items] Private Education Loans deferred origination costs and unamortized premium/(discount), Year 2 Net Unamortized Premium Or Discount, Originated In Fiscal Year Before Latest Fiscal Year Net Unamortized Premium Or Discount, Originated In Fiscal Year Before Latest Fiscal Year Total Private Education Loans, gross, After Year 5 Loans Gross, Originated Five Years Before Latest Fiscal Year Loans Gross, Originated Five Years Before Latest Fiscal Year Total assets Assets Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Asset, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration] Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Asset, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration] 2024 Share Repurchase Program 2024 Share Repurchase Program [Member] 2024 Share Repurchase Program Total interest expense Interest Expense, Operating Total Private Education Loans in forbearance, Year 3 Financing Receivable, Loans In Forbearance, Year Three, Originated, Two Years before Current Fiscal Year Financing Receivable, Loans In Forbearance, Year Three, Originated, Two Years before Current Fiscal Year Variable Interest Entity, Not Primary Beneficiary Variable Interest Entity, Not Primary Beneficiary [Member] Current period recoveries, After Year 5 Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery, Originated Five Or More Years Before Current Fiscal Year Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery, Originated Five Or More Years Before Current Fiscal Year Total Private Education Loans in Repayment, After Year 5 Loans In Repayment, Originated Five Or More Years Before Current Fiscal Year Loans In Repayment, Originated Five Or More Years Before Current Fiscal Year Nitro Nitro College [Member] Nitro College Gross Unrealized Gains Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax PEO PEO [Member] Deposits - non-interest-bearing Noninterest-Bearing Deposit Liabilities Total Total Debt, Long-Term and Short-Term, Combined Amount Increase in trading investments Payments To Acquire Trading Securities Held-For-Sale Payments To Acquire Trading Securities Held-For-Sale Goodwill Goodwill Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Number of government sponsored securities with unrealized losses Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions Retained Earnings Retained Earnings [Member] Total operating expenses Operating Expenses 2039 Maturity 2039 [Member] Maturity 2039 [Member] Beginning balance (in shares) Ending balance (in shares) Common Stock, Shares, Outstanding Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Award Timing Disclosures [Line Items] Fair Values of Financial Assets and Liabilities, Including Derivative Financial Instruments Fair Value, by Balance Sheet Grouping [Table Text Block] Financing Receivable, Past Due [Line Items] Financing Receivable, Past Due [Line Items] Diluted earnings per common share (in dollars per share) Earnings Per Share, Diluted FDIC assessment fees Federal Deposit Insurance Corporation Premium Expense Accrued interest capitalized during the period Interest Costs Capitalized Acquired intangible assets amortization expense Intangible Asset, Finite-Lived, Amortization Expense Series B: 2.5 million and 2.5 million shares issued, respectively, at stated value of $100 per share Preferred Stock, Value, Outstanding Intangible Asset, Finite-Lived [Line Items] Intangible Asset, Finite-Lived [Line Items] Floating Rate Non-Cumulative Preferred Stock, Series B, par value $.20 per share Floating Rate Non-Cumulative Preferred Stock, Series B, par value $.20 per share [Member] Floating Rate Non-Cumulative Preferred Stock, Series B, par value $.20 per share Year 4 Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year Estimated weighted average life of student loans Estimated Weighted Average Life Of Student Loans Estimated weighted average life of student loans. Schedule of Offsetting Assets Offsetting Assets [Table Text Block] Provisions for loan losses Financing Receivable, Credit Loss, Expense (Reversal), New Commitments Financing Receivable, Credit Loss, Expense (Reversal), New Commitments Private Education Loans, net, Year 4 Financing Receivable, after Allowance for Credit Loss, Originated Three Years Before Current Fiscal Year Financing Receivable, after Allowance for Credit Loss, Originated Three Years Before Current Fiscal Year Total accrued interest by origination vintage, Year 4 Financing Receivable, Accrued interest, Origination Vintage, Originated Three Years before Latest Fiscal Year Financing Receivable, Accrued interest, Origination Vintage, Originated Three Years before Latest Fiscal Year Qtr.-End Weighted Average Stated Rate Weighted Average Rate Domestic Deposit Liabilities [Abstract] Loans Carrying Amount Of Assets Securing Debt Outstanding Loans Carrying Amount Of Assets Securing Debt Outstanding Loans Earning assets: Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] Current period recoveries, Year 5 Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery, Originated Four Years Before Current Fiscal Year Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery, Originated Four Years Before Current Fiscal Year Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Total Private Education Loans in forbearance Financing Receivable, Loans In Forbearance, before Allowance for Credit Loss Financing Receivable, Loans In Forbearance, before Allowance for Credit Loss (Decrease) increase in accrued interest payable Increase (Decrease) in Interest Payable, Net Net position Derivative Liability, Including Not Subject to Master Netting Arrangement, after Offset and Deduction Total Derivative, Gain (Loss) on Derivative, Net 2055 Maturity 2055 [Member] Maturity 2055 Gross Proceeds Proceeds from Issuance of Debt Collateral [Axis] Collateral Held [Axis] Senior Unsecured Notes Due November 2, 2026 Senior Unsecured Notes Due November 2, 2026 [Member] Senior Unsecured Notes Due November 2, 2026 Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Transfer - funded loans Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability, Commitments Funded Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability, Commitments Funded Net decrease in other deposits Net Increase In NOW Account Deposits Net Increase In NOW Account Deposits 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] Schedule of Allowance for Credit Losses and Recorded Investments in Loans Financing Receivable, Allowance for Credit Loss [Table Text Block] Common stock, shares issued (in shares) Beginning balance, Common shares issued (in shares) Ending balance, Common shares issued (in shares) Common Stock, Shares, Issued Current period gross charge-offs, Year 5 Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Writeoff, Originated Four Years Before Latest Fiscal Year Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Writeoff, Originated Four Years Before Latest Fiscal Year Balance, beginning of period Balance, end of period Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Entity Information [Line Items] Entity Information [Line Items] Total Private Education Loans in Repayment, Year 3 Loans In Repayment, Originated Two Years Before Current Fiscal Year Loans In Repayment, Originated Two Years Before Current Fiscal Year 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. Allowance for credit losses Debt Securities, Available-for-Sale, Allowance for Credit Loss Scholly, Inc. Scholly, Inc. [Member] Scholly, Inc. Deposits exceeding FDIC insurance limits Cash, Uninsured Amount Gross Unrealized Losses Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Class of Stock [Line Items] Class of Stock [Line Items] Non-interest expenses: Noninterest Expense [Abstract] Seasoning based on monthly scheduled payments due from more than 48 payments 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 Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Loan Deferment Loan Deferment [Member] Loan Deferment Period-end Amortized Cost Basis Financing Receivable, Modified, Subsequent Default Termination Date Trading Arrangement Termination Date 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] Subsequent Events [Abstract] Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Net position Derivative Asset, Including Not Subject to Master Netting Arrangement, after Offset and Deduction 2053 Maturity 2053 [Member] Maturity 2053 2050 Maturity 2050 [Member] Maturity 2050 Fair Value as of Grant Date Award Grant Date Fair Value Debt instrument, redemption price, percentage Debt Instrument, Redemption Price, Percentage Schedule of Available-for-Sale Securities, Continuous Unrealized Loss Position, Fair Value Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value [Table Text Block] Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Remaining authority under the share repurchase program Share Repurchase Program, Remaining Authorized, Amount Arrangement Duration Trading Arrangement Duration Deferred origination costs and unamortized premium/(discount) Financing Receivable, Unamortized Loan Cost (Fee) and Purchase Premium (Discount) Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Registrant Name Entity Registrant Name Lendable value of collateral Lendable Value Of Collateral Lendable Value Of Collateral Gross Unrealized Losses Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Cost Basis Intangible Asset, Finite-Lived, before Accumulated Amortization Total Private Education Loans, Year 4 Loans, Originated Three Years Before Latest Fiscal Year Loans, Originated Three Years Before Latest Fiscal Year Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Loan Restructuring Modification [Axis] Loan Restructuring Modification [Axis] Intangible Asset, Finite-Lived, Class [Domain] Intangible Asset, Finite-Lived, Class [Domain] 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] All Award Types Award Type [Domain] Brokered deposit placement fee Brokered Deposit Placement Fee Brokered Deposit Placement Fee Fair Value Measurements Fair Value Disclosures [Text Block] Level 3  Fair Value, Inputs, Level 3 [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] Common stock repurchased under repurchase programs (in shares) Common stock repurchased (in shares) Treasury Stock, Shares, Acquired Expected amortization of 2026 Intangible Asset, Finite-Lived, Estimated Amortization Expense, Year One Common stock closing price (in dollars per share) Share Price Capitalized interest Financing Receivable, Held For Sale, Capitalized Interest Financing Receivable, Held For Sale, Capitalized Interest Low income housing tax credit investments, expected tax benefits recognized Affordable Housing Tax Credits And Other Tax Benefits, Percentage Affordable Housing Tax Credits And Other Tax Benefits, Percentage Other assets Other Assets, Net Other Assets Loan delinquent 30-59 days Financial Asset, 30 to 59 Days Past Due [Member] Financing Receivable, Modified, Subsequent Default Financing Receivable, Modified, Subsequent Default [Table Text Block] 2051 Maturity 2051 [Member] Maturity 2051 Carrying Amount of the Hedged Assets/(Liabilities) Hedged Liability, Fair Value Hedge Liability Class [Axis] Liability Class [Axis] Total Capital (to Risk-Weighted Assets) Banking Regulation, Total Capital, Actual Common stock repurchased, amount Treasury Stock, Value, Acquired, Cost Method Non-interest income: Noninterest Income [Abstract] Cash, cash equivalents and restricted cash at beginning of period Cash, cash equivalents and restricted cash at end of period Total cash, cash equivalents and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Cash collateral pledged Derivative Liability, Subject to Master Netting Arrangement, Collateral, Right to Reclaim Cash Not Offset Schedule of Finite-Lived Intangible Assets [Table] Intangible Asset, Finite-Lived [Table] Non-NEOs Non-NEOs [Member] Financing Receivable, Allowance for Credit Loss [Roll Forward] Financing Receivable, Allowance for Credit Loss [Roll Forward] Total Private Education Loans, gross, Year 4 Loans Gross, Originated Three Years Before Latest Fiscal Year Loans Gross, Originated Three Years Before Latest Fiscal Year Expected amortization of 2027 Intangible Asset, Finite-Lived, Estimated Amortization Expense, Year Two Total Available-For-Sale Securities, Unrealized Loss Position [Abstract] Available-For-Sale Securities, Unrealized Loss Position [Abstract] Schedule of Debt Schedule of Debt [Table Text Block] SMB Private Education Loan Trust 2026 SMB Private Education Loan Trust 2026 [Member] SMB Private Education Loan Trust 2026 Percentage of Private Education Loans in repayment, Year 5 Percentage Of Loans In Repayment, Originated Four Years Before Latest Fiscal Year Percentage Of Loans In Repayment, Originated Four Years Before Latest Fiscal Year Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Common stock repurchased Payments for Repurchase of Common Stock Mortgage-backed securities Collateralized Mortgage-Backed Securities [Member] Statistical Measurement [Axis] Statistical Measurement [Axis] Schedule of Impact of Derivatives on the Consolidated Statements of Income Derivative Instruments, Gain (Loss) [Table Text Block] Gains (losses) on securities, net Losses on securities, net Gain (Loss) on Sales of Mortgage-Backed Securities (MBS) Award Type Award Type [Axis] Amount of gain (loss) recognized in other comprehensive income (loss) Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax FICO at Origination School Fico [Member] School type fico credit quality indicators that are developed and used internally by the company. Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Money market Weighted Average Rate Domestic Deposit, Money Market Retained earnings Retained Earnings (Accumulated Deficit) Consumer Portfolio Segment Consumer Portfolio Segment [Member] Fixed-rate Fixed-rate Fixed Income Interest Rate [Member] Schedule of Securities Financing Transactions Schedule of Securities Financing Transactions [Table Text Block] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Common Stock Common Stock [Member] Available-for-sale investments at fair value (cost of $1,775,289 and $1,812,408, respectively) Estimated Fair Value Available-for-sale investments Debt Securities, Available-for-Sale Savings Weighted Average Rate Domestic Deposit, Savings Seasoning based on monthly scheduled payments due from 13 - 24 payments 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. Change in unrealized gains or losses for the period included in other comprehensive income for assets held at the end of the reporting period Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI Series B Preferred Stock Series B Preferred Stock [Member] Derivative Contract [Domain] Derivative Contract [Domain] Line of credit facility, interest holding percentage Line of Credit Facility, Interest Holding Percentage Line of Credit Facility, Interest Holding Percentage Delinquent Private Education Loans in repayment as a percentage of Private Education Loans in repayment, Year 5 Delinquencies As Percentage Of Loans In Repayment, Originated Four Years Before Current Fiscal Year Delinquencies As Percentage Of Loans In Repayment, Originated Four Years Before Current Fiscal Year Total liabilities and equity Liabilities and Equity Goodwill and acquired intangible assets, net Intangible Asset, Including Goodwill, after Accumulated Amortization Employee Stock Option Share-Based Payment Arrangement, Option [Member] Securities Financing Transaction [Table] Security Financing Transaction [Table] Segments [Axis] Segments [Axis] Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Asset Class [Axis] Asset Class [Axis] Schedule of Cumulative Basis Adjustments for Fair Value Hedges Schedule of Fair Value Hedging Instruments, Statements of Financial Performance and Financial Position, Location [Table Text Block] Trading investments at fair value (cost of $37,986 and $37,606, respectively) Trading investments Debt Securities, Trading Tabular List, Table Tabular List [Table Text Block] Additional paid-in capital Additional Paid in Capital Expected amortization of 2028 Intangible Asset, Finite-Lived, Estimated Amortization Expense, Year Three Par value of mortgage-backed securities pledged to FRB Par Value Of Mortgage-Backed Securities Pledged To FRB Par Value Of Mortgage-Backed Securities Pledged To FRB Name Awards Close in Time to MNPI Disclosures, Individual Name Total change in other comprehensive income (loss) for unrealized gains (losses) on derivatives, before income tax (expense) benefit Change In Other Comprehensive Income (Loss) For Unrealized Gains (Losses) On Derivatives, Before Income Tax (Expense) Benefit Change In Other Comprehensive Income (Loss) For Unrealized Gains (Losses) On Derivatives, Before Income Tax (Expense) Benefit 700-749 FICO score 700-749 [Member] FICO score 700-749 [Member] Transfer from allowance for unfunded loan commitments Off-Balance Sheet, Credit Loss, Liability, Transfer From Unfunded Commitments Off-Balance Sheet, Credit Loss, Liability, Transfer From Unfunded Commitments Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Axis] Net proceeds from sales of loans held for investment and loans held for sale Net Proceeds from Loans Held for Investment and Loans Held for Sale Net Proceeds from Loans Held for Investment and Loans Held for Sale 2038 Maturity 2038 [Member] Maturity 2038 [Member] Adjustment to Compensation: Adjustment to Compensation [Axis] Money-market and savings accounts Money Market and Savings Accounts [Member] Money Market and Savings Accounts [Member] Stable interest-bearing deposits, total Stable Interest-Bearing Deposits, Total Stable Interest-Bearing Deposits, Total Total operating expenses Operating Expenses, Excluding Amortization Of Intangible Assets Operating Expenses, Excluding Amortization Of Intangible Assets Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Interest Interest Paid, Excluding Capitalized Interest, Operating Activity Hedging Designation [Axis] Hedging Designation [Axis] Loan delinquent 60-89 days Financial Asset, 60 to 89 Days Past Due [Member] 2025-A ABS Transaction SMB Private Education Loan Trust 2025-A [Member] SMB Private Education Loan Trust 2025-A Credit Facility [Axis] Credit Facility [Axis] Private Education Loans Private Education Loans Private Education Loans [Member] Private education loans. Total earning assets Total Assets, Fair Value Disclosure Name Measure Name Pay vs Performance Disclosure [Line Items] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] Unfunded loan commitments for loans held for investment Beginning balance Ending balance Fair Value Disclosure, off-Balance-Sheet Risks, Amount, Liability Debt Instrument [Line Items] Debt Instrument [Line Items] Average Balance Financing Receivable, Before Allowance For Credit Loss, Average Balance Financing Receivable, Before Allowance For Credit Loss, Average Balance Loans Interest and Fee Income, Financing Receivable Additional Paid-In Capital Additional Paid-in Capital [Member] Total Allowance Percentage of Private Education Loan Exposure Allowance As Percentage Of Ending Loan Balance And Accrued Interest Allowance As Percentage Of Ending Loan Balance And Accrued Interest Other interest-earning assets Other Interest Earning Assets Accrued interest receivable Total accrued interest receivable Interest Receivable Name Trading Arrangement, Individual Name Cash and cash equivalents Cash and cash equivalents Cash and Cash Equivalent Amortization of Secured Borrowing Facility upfront fee Amortization of ABCP Upfront Loan Fees Amortization of ABCP Upfront Loan Fees Company Selected Measure Amount Company Selected Measure Amount Income taxes receivable, net Income Taxes Receivable Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Accounts and Financing Receivables [Table] Without cosigner Without Cosigner [Member] Without Cosigner [Member] Allowance For Credit Losses [Abstract] Allowance For Credit Losses [Abstract] Allowance for credit losses. Allowance Allowance [Abstract] Allowance. Non-PEO NEO Non-PEO NEO [Member] U.S. Basel III Minimum Requirements Plus Buffer, Amount Banking Regulation, Tier 1 Leverage Capital [Abstract] Total non-interest expenses Noninterest Expense Interest recognized on derivatives Gain (Loss) on Fair Value Hedges Recognized in Earnings Effect of dilutive securities: Dilutive Securities, Effect on Basic Earnings Per Share [Abstract] Award Timing Method Award Timing Method [Text Block] Net increase (decrease) in cash, cash equivalents and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Common Equity Tier 1 Capital (to Risk-Weighted Assets) Tier One Common Equity Capital to Risk Weighted Assets Tier One Common Equity Capital to Risk Weighted Assets Net income Net income Net Income (Loss) Attributable to Parent Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Financing Receivable, Past Due [Table] Financing Receivable, Past Due [Table] Restatement Determination Date: Restatement Determination Date [Axis] Private Education Loans deferred origination costs and unamortized premium/(discount), Year 1 Net Unamortized Premium Or Discount, Originated In Current Fiscal Year Net Unamortized Premium Or Discount, Originated In Current Fiscal Year Schedule of Derivative Instruments, Effect on Other Comprehensive Income (Loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Trading Activity [Axis] Trading Activity [Axis] Acquired intangible assets amortization expense Acquired intangible assets amortization expense Amortization of Acquired Intangible Assets, Including Impairment of Intangible Assets Amortization of Acquired Intangible Assets, Including Impairment of Intangible Assets Total Private Education Loans sold Financing Receivable, Sale Private Education Loans deferred origination costs and unamortized premium/(discount) Net Unamortized Premium Or Discount, Before Allowance For Credit Loss Net Unamortized Premium Or Discount, Before Allowance For Credit Loss Total Private Education Loans, gross, Year 1 Loans Gross, Originated In Current Fiscal Year Loans Gross, Originated In Current Fiscal Year Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Statistical Measurement [Domain] Statistical Measurement [Domain] Total Private Education Loans, gross, Year 3 Loans Gross, Originated Two Years Before Latest Fiscal Year Loans Gross, Originated Two Years Before Latest Fiscal Year Document Fiscal Year Focus Document Fiscal Year Focus Impact of master netting agreement Derivative Liability, Subject to Master Netting Arrangement, Asset Offset Loan principal Financing Receivable Held For Sale, Principal Financing Receivable Held For Sale, Principal FICO Refreshed School FICO, Refreshed Amounts [Member] School FICO, Refreshed Amounts [Member] Total allowance for credit losses, ending balance Allowance for Credit Loss, Excluding Accrued Interest Allowance for Credit Loss, Excluding Accrued Interest Deposits Total deposits Deposits Common stock, par value $0.20 per share, 1.125 billion shares authorized: 445.7 million and 443.2 million shares issued, respectively Common Stock, Value, Issued Numerator: Numerator [Abstract] Numerator. Amount of gain (loss) reclassified from accumulated other comprehensive income into interest expense Interest Expense, Operating and Nonoperating Line of Credit Line of Credit [Member] Restatement Determination Date Restatement Determination Date Cash collateral pledged Derivative Asset, Subject to Master Netting Arrangement, Collateral, Obligation to Return Cash, Offset Against Derivative Asset Brokered deposit placement fee Cash Paid For Brokered Deposit Placement Fee Cash Paid For Brokered Deposit Placement Fee Preferred stock dividend rate (in dollars per share) Preferred Stock, Dividend Rate, Per-Dollar-Amount Other operating expenses Other Noninterest Expense Total in percent Private Education Loans Gross, Percentage Private education loans gross in percent. Total Private Education Loans in repayment Loans In Repayment, Before Allowance For Credit Loss Loans In Repayment, Before Allowance For Credit Loss Amendment Flag Amendment Flag Schedule of Notional Amounts of Outstanding Derivative Positions Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] Gross Unrealized Losses Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax Number of mortgage-backed securities Debt Securities, Available-For-Sale, Number Of Positions Debt Securities, Available-For-Sale, Number Of Positions Short-term borrowings, difference Short-term Debt, Fair Value, Difference Between Carrying Value and Fair Value Short-term Debt, Fair Value, Difference Between Carrying Value and Fair Value Investments [Domain] Investments [Domain] 670-699 FICO score 670-699 [Member] FICO score 670-699 [Member] Derivative, fair value, amount offset against collateral, net Derivative, Fair Value, Amount Offset Against Collateral, Net Total accrued interest by origination vintage, Year 3 Financing Receivable, Accrued interest, Origination Vintage, Originated Two Years before Latest Fiscal Year Financing Receivable, Accrued interest, Origination Vintage, Originated Two Years before Latest Fiscal Year Student Loan Student Loan [Member] Accrued interest receivable not expected to be capitalized Accrued Interest Receivable Not Expected To Be Capitalized Accrued Interest Receivable Not Expected To Be Capitalized Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Tier 1 Capital (to Risk-Weighted Assets) Banking Regulation, Tier 1 Risk-Based Capital, Well Capitalized, Minimum Transfers into level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 Entity Address, State or Province Entity Address, State or Province PEO Total Compensation Amount PEO Total Compensation Amount Low income housing tax credit investments Investment, Proportional Amortization Method, Elected, Amount Assets: Assets, Fair Value Disclosure [Abstract] With and without cosigners Cosigner [Member] Cosigner credit quality indicators that are developed and used internally by the company. Share Repurchase Program [Domain] Share Repurchase Program [Domain] Notional value Notional Values Derivative, Notional Amount Average common shares outstanding (in shares) Weighted average shares used to compute basic EPS (in shares) Weighted Average Number of Shares Outstanding, Basic Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Total Private Education Loans, Year 1 Loans, Originated In Current Fiscal Year Loans, Originated In Current Fiscal Year Provisions for credit losses reported in consolidated statements of income Financing Receivable, Credit Loss, Expense (Reversal), Commitments Financing Receivable, Credit Loss, Expense (Reversal), Commitments Investments: Investments [Abstract] 2027 Maturity 2027 [Member] Maturity 2027 Net decrease in loans held for investment and loans held for sale (other than loans acquired and originated, and loan sales) Net Decrease in Loans Held for Investment and Loans Held for Sale Net Decrease in Loans Held for Investment and Loans Held for Sale Increase in accrued interest receivable Increase (Decrease) in Accrued Interest Receivable, Net Total non-interest income Noninterest Income Trading investments received in consideration for loans sold Trading Investment Received in Consideration for Loans Sold Trading Investment Received in Consideration for Loans Sold Current period net charge-offs, Year 2 Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery, Originated In Fiscal Year Before Latest Fiscal Year Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery, Originated In Fiscal Year Before Latest Fiscal Year Loans Held for Investment Loans Held for Sale Loans, Notes, Trade and Other Receivables Disclosure [Text Block] 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. Total Time Deposits Total Interest Receivable Accrued Interest Receivable On Private Education Loans Accrued interest receivable on private education loans. Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Preferred stock dividends paid Payments of Ordinary Dividends, Preferred Stock and Preference Stock Class of Stock [Axis] Class of Stock [Axis] Net income attributable to SLM Corporation common stock Net Income (Loss) Available to Common Stockholders, Basic 2048 Maturity 2048 [Member] Maturity 2048 [Member] SMB Private Education Loan Trust 2025 SMB Private Education Loan Trust 2025 [Member] SMB Private Education Loan Trust 2025 Accumulated Amortization Intangible Asset, Finite-Lived, Accumulated Amortization Secured borrowing facility maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Less than 670 FICO score less than 670 [Member] FICO score less than 670 [Member] Banking and Thrift, Other Disclosure [Abstract] Banking and Thrift, Other Disclosure [Abstract] Total Private Education Loans Loans, Before Allowance For Credit Loss Loans, Before Allowance For Credit Loss Loans held for investment (net of allowance for losses of $1,354,014 and $1,430,318, respectively) Private Education Loans, net Financing Receivable, Excluding Accrued Interest, after Allowance for Credit Loss Private Education Loans deferred origination costs and unamortized premium/(discount), After Year 5 Net Unamortized Premium Or Discount, Originated Five Or More Years Before Latest Fiscal Year Net Unamortized Premium Or Discount, Originated Five Or More Years Before Latest Fiscal Year Recently Issued Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Unsecured borrowings Unsecured Debt [Member] Total unrealized (losses) gains Other Comprehensive Income (Loss), before Tax Long-term borrowings Long-Term Long-Term Debt Private Education Loans, net, Year 1 Financing Receivable, after Allowance for Credit Loss, Originated In Current Fiscal Year Financing Receivable, after Allowance for Credit Loss, Originated In Current Fiscal Year Decrease in income taxes payable, net Increase (Decrease) in Income Taxes Payable Year 3 Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year Vertical risk retention interest Vertical Risk Retention, Percentage Vertical Risk Retention, Percentage Total net cash provided by investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Stockholders' Equity Equity [Text Block] Security Exchange Name Security Exchange Name Seasoning based on monthly scheduled payments due from 25 - 36 payments 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 Valuation Approach and Technique [Axis] Valuation Approach and Technique [Axis] Actual Amount Banking Regulation, Total Capital [Abstract] Delinquent Private Education Loans in repayment as a percentage of Private Education Loans in repayment, Year 2 Delinquencies As Percentage Of Loans In Repayment, Originated In Fiscal Year Before Latest Fiscal Year Delinquencies As Percentage Of Loans In Repayment, Originated In Fiscal Year Before Latest Fiscal Year Accrued interest on deposits Interest Payable, Current Estimated Fair Value Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer Total Private Education Loans, After Year 5 Loans, Originated Five Or More Years Before Latest Fiscal Year Loans, Originated Five Or More Years Before Latest Fiscal Year Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Current period recoveries, Year 3 Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery, Originated Two Years Before Current Fiscal Year Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery, Originated Two Years Before Current Fiscal Year Name Outstanding Recovery, Individual Name Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Threshold period when delinquent loans are written off Threshold Period Past Due For Write-off Of Financing Receivable Threshold Period Past Due For Write-off Of Financing Receivable 60 Days or Greater Past Due Financial Asset, Equal To Or Greater Than 60 Days Past Due [Member] Financial Asset, Equal To Or Greater Than 60 Days Past Due Average loans in repayment Allowance Coverage Of Charge Offs Average Loans In Repayment Allowance coverage of charge offs average loans in repayment. Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Debt Outstanding Debt, Long-Term and Short-Term, Combined Amount [Abstract] Interest expense on long-term borrowings Interest Expense, Long-Term Debt Supplemental non-cash investing activities: Noncash Investing and Financing Items [Abstract] Unrealized (gains) losses on derivatives and hedging activities, net Unrealized Gain (Loss) on Derivatives Actual Ratio Banking Regulation, Risk-Based Information [Abstract] 2052 Maturity 2052 [Member] Maturity 2052 Schedule of Certificates of Deposit Maturities Time Deposit Maturities [Table Text Block] Available For Sale - Debt Securities Debt Securities [Member] 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. Asset Class [Domain] Asset Class [Domain] Credit Score, FICO [Axis] Credit Score, FICO [Axis] Compensation Amount Outstanding Recovery Compensation Amount Average contractual rate Financing Receivable, Change in Contractual Rate Financing Receivable, Change in Contractual Rate Individual: Individual [Axis] Average common and common equivalent shares outstanding (in shares) Weighted average shares used to compute diluted EPS (in shares) Weighted Average Number of Shares Outstanding, Diluted Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] After one to two years Time Deposit Maturities, Rolling Year Two Entity Emerging Growth Company Entity Emerging Growth Company Total Private Education Loans in Repayment, Year 5 Loans In Repayment, Originated Four Years Before Current Fiscal Year Loans In Repayment, Originated Four Years Before Current Fiscal Year Total Private Education Loans, gross Loan type Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss Underlying Security Market Price Change Underlying Security Market Price Change, Percent Derivative Financial Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Short-term borrowings Short-Term Short-Term Debt Gross position Derivative Liability, Subject to Master Netting Arrangement, before Offset Brokered deposits Brokered Deposits Brokered Deposits Provision Off-Balance-Sheet, Credit Loss, Liability, Credit Loss Expense (Reversal) Defaulted Amount Financing receivable, modified in period, amount Financing Receivable, Modified in Period, Amount Percentage of Private Education Loans in repayment, Year 3 Percentage Of Loans In Repayment, Originated Two Years Before Latest Fiscal Year Percentage Of Loans In Repayment, Originated Two Years Before Latest Fiscal Year Treasury Stock Treasury Stock, Common [Member] Delinquent Private Education Loans in repayment as a percentage of Private Education Loans in repayment Delinquencies As Percentage Of Loans In Repayment Delinquencies as a percentage of loans in repayment. Intangible Asset, Goodwill and Other [Abstract] Money market Interest-Bearing Domestic Deposit, Money Market Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-Sale [Line Items] Unsecured debt repaid Repayment of unsecured debt Repayments of Unsecured Debt Interest Rate Reduction Interest Rate Below Market Reduction [Member] Unsecured debt issued Proceeds from Issuance of Unsecured Debt Transfers and Servicing [Abstract] Collateral [Domain] Collateral Held [Domain] Loans sold Financing Receivable And Off-Balance Sheet, Excluding Accrued Interest, Before Allowance For Credit Loss, Loan Sold Financing Receivable And Off-Balance Sheet, Excluding Accrued Interest, Before Allowance For Credit Loss, Loan Sold All Executive Categories All Executive Categories [Member] Provision/New commitments - net Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability, Additional Commitments Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability, Additional Commitments Valuation Approach and Technique [Domain] Valuation Approach and Technique [Domain] Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Financing receivable, transfer to held-for-sale, allowance for credit loss, expense reversal Financing Receivable, Transfer to Held-for-Sale, Allowance for Credit Loss, Expense Reversal Credit Quality Indicators [Domain] Credit Quality Indicators [Domain] Credit Quality Indicators [Domain] Reconciliation of the Consolidated Statements of Cash Flows to the Consolidated Balance Sheets: Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation [Abstract] Settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements Technology expenses Information Technology and Data Processing 2056 Maturity 2056 [Member] Maturity 2056 Schedule of Earnings Per Share, Basic and Diluted Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Trading investments, cost Debt Securities, Trading, Amortized Cost Denominator: Denominator [Abstract] Denominator [Abstract] Schedule of Amortized Cost Basis of Financing Receivables Financing Receivables, Amortized Cost Basis [Table Text Block] Financing Receivables, Amortized Cost Basis Debt Disclosure [Abstract] Debt Disclosure [Abstract] Segment Reporting Segment Reporting [Text Block] Minimum Minimum [Member] Private Education Loan term securitizations Private Education Loan Securitization [Member] Private Education Loan Securitization [Member] Investment Type [Axis] Investment Type [Axis] Available-for-sale investments Investments, Fair Value Disclosure Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] 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 Liabilities Liabilities [Abstract] Location, Statement of Income, Balance [Axis] Location, Statement of Income, Balance [Axis] 2049 Maturity 2049 [Member] Maturity 2049 [Member] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] After five years Time Deposit Maturities, after Rolling Year Five Total accrued interest by origination vintage, Year 2 Financing Receivable, Accrued Interest, Origination Vintage, Originated in Fiscal Year before Latest Fiscal Year Financing Receivable, Accrued Interest, Origination Vintage, Originated in Fiscal Year before Latest Fiscal Year Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Total interest-bearing liabilities Financial Liabilities Fair Value Disclosure Other liabilities Other Liabilities Other income Noninterest Income, Other Operating Income After four to five years Time Deposit Maturities, Rolling Year Five Financing Receivable, Allowance for Credit Loss [Table] Financing Receivable, Allowance for Credit Loss [Table] Common stock, shares authorized (in shares) Common Stock, Shares Authorized Percent of total notional derivative contracts Derivative Instrument, Percent Of Total Notional Derivative Contracts Derivative Instrument, Percent Of Total Notional Derivative Contracts Weighted Average Useful Life (in years) Intangible Asset, Finite-Lived, Useful Life Gain on Sale for Additional Loans Transferred by Bank Debt Securities, Available-for-Sale, Realized Gain Exercise Price Award Exercise Price Fair Value Measurements on a Recurring Basis Fair Value, Recurring [Member] Segment Reporting [Line Items] Segment Reporting [Line Items] Aggregate purchase price (not to exceed) Share Repurchase Program, Authorized, Amount Total Private Education Loans in forbearance, Year 4 Financing Receivable, Loans In Forbearance, Year Four, Originated, Three Years before Current Fiscal Year Financing Receivable, Loans In Forbearance, Year Four, Originated, Three Years before Current Fiscal Year Percentage of Private Education Loans in repayment Percentage Of Loans In Repayment, Before Allowance For Credit Loss Percentage Of Loans In Repayment, Before Allowance For Credit Loss Document Quarterly Report Document Quarterly Report Total accrued interest by origination vintage, Year 5 Financing Receivable, Accrued interest, Origination Vintage, Originated Four Years before Latest Fiscal Year Financing Receivable, Accrued interest, Origination Vintage, Originated Four Years before Latest Fiscal Year Current period recoveries, Year 5 Financing Receivable, Allowance for Credit Loss, Recovery, Originated Four Years Before Current Fiscal Year Financing Receivable, Allowance for Credit Loss, Recovery, Originated Four Years Before Current Fiscal Year Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] Available-for-sale investments received in consideration for loans sold Available-For-Sale Investments Received in Consideration for Loans Sold Available-For-Sale Investments Received in Consideration for Loans Sold Schedule of Deposits Schedule Of Deposits [Table Text Block] Schedule of Deposits [Table Text Block] Regulatory Capital Regulatory Capital Requirements under Banking Regulations [Text Block] Loans Transferred to the Trust by Third-Party Seller Proceeds from Sale of Debt Securities, Available-for-Sale Deposits Deposits [Member] Repayments of long-term debt Repayments of Long-Term Debt Preferred stock, liquidation preference (in dollars per share) Preferred Stock, Liquidation Preference Per Share Other Liabilities Derivative Liability [Abstract] Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Equity Component [Domain] Equity Component [Domain] Measurement Input Type [Domain] Measurement Input Type [Domain] Included in earnings (or changes in net assets) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Loans held for investment, net Loans Receivable, Fair Value Disclosure Accrued interest payable Accrued Liabilities, Fair Value Disclosure Adoption Date Trading Arrangement Adoption Date Securities Financing Transaction [Line Items] Securities Financing Transaction [Line Items] Delinquent Private Education Loans in repayment as a percentage of Private Education Loans in repayment, Year 3 Delinquencies As Percentage Of Loans In Repayment, Originated Two Years Before Current Fiscal Year Delinquencies As Percentage Of Loans In Repayment, Originated Two Years Before Current Fiscal Year Title Trading Arrangement, Individual Title Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Maximum amount of forbearance granted Financing Receivable, Month Limit On Forbearance Granted, Life Of Loan Financing Receivable, Month Limit On Forbearance Granted, Life Of Loan Accounting Policies [Abstract] Accounting Policies [Abstract] Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Interest expense on short-term borrowings Interest Expense, Short-Term Borrowings Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Liability for unfunded commitments Investment Program, Proportional Amortization Method, Elected, Commitment 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] Business Combination [Domain] Business Combination [Domain] Cash Flow Hedges Effect of Cash Flow Hedges on Results of Operations [Abstract] Commitments, Contingencies and Guarantees Commitments and Contingencies Disclosure [Text Block] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Financial Asset, Period Past Due [Domain] Financial Asset, Aging [Domain] Weighted Average Weighted Average [Member] Private Education Loans, net, Year 5 Financing Receivable, after Allowance for Credit Loss, Originated Four Years Before Current Fiscal Year Financing Receivable, after Allowance for Credit Loss, Originated Four Years Before Current Fiscal Year All Adjustments to Compensation All Adjustments to Compensation [Member] Business Combination [Axis] Business Combination [Axis] Total net cash used in operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Income Statement [Abstract] Income Statement [Abstract] Equity Equity, Attributable to Parent [Abstract] Document Transition Report Document Transition Report Loans in forbearance as a percentage of loans in repayment and forbearance, Year 4 Loans In Forbearance As A Percentage Of Private Education Loans In repayment And Forbearance, Originated Three Years Before Current Fiscal Year Loans In Forbearance As A Percentage Of Private Education Loans In repayment And Forbearance, Originated Three Years Before Current Fiscal Year Accrued interest receivable Accrued Interest Receivable, Fair Value Disclosure Accrued Interest Receivable, Fair Value Disclosure Loans In forbearance Loans In Forbearance [Member] Loans In Forbearance Private Education Loans allowance for losses, Year 3 Financing Receivable, Allowance For Credit Loss, Originated Two Years Before Current Fiscal Year Financing Receivable, Allowance For Credit Loss, Originated Two Years Before Current Fiscal Year Operating expenses: Operating Expenses [Abstract] Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Schedule of Acquired Intangible Assets Intangible Asset, Finite-Lived [Table Text Block] Cash dividends declared: Dividends, Cash [Abstract] Credit Quality Indicators [Axis] Credit Quality Indicators [Axis] Credit Quality Indicators [Axis] Issuance of common shares Stock Issued During Period, Value, New Issues Including Dividend Equivalents Stock Issued During Period, Value, New Issues Including Dividend Equivalents City Area Code City Area Code Private education loans at origination Private Education Loans At Origination Private Education Loans At Origination Subsequent Events Subsequent Events [Text Block] Residual Interests Debt Securities, Trading, Measurement Input Name Forgone Recovery, Individual Name Non-marketable securities investment Other Investment Not Readily Marketable, Fair Value Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Capitalized interest Financing Receivable, Sale, Capitalized Interest Financing Receivable, Sale, Capitalized Interest Common stock, par value $.20 per share Common stock, par value $.20 per share [Member] Common stock, par value $.20 per share Total interest income Interest and Dividend Income, Operating Increase in other assets Increase (Decrease) in Other Operating Assets Common Equity Tier 1 Capital (to Risk-Weighted Assets) Tier One Common Equity Capital Required To Be Well Capitalized To Risk Weighted Assets Tier One Common Equity Capital Required To Be Well Capitalized To Risk Weighted Assets Common shares issued (in shares) Stock Issued During Period, Shares, New Issues Ending loans in repayment Allowance Coverage Of Charge Offs Ending Loans In Repayment Allowance coverage of charge-offs Ending loans in repayment. Total Capital (to Risk-Weighted Assets) Banking Regulation, Total Risk-Based Capital, Well Capitalized, Minimum Measurement Basis [Axis] Measurement Basis [Axis] Impact of master netting agreement Derivative Asset, Subject to Master Netting Arrangement, Liability Offset Common stock repurchased (in shares) Stock Repurchased and Retired During Period, Shares Total Private Education Loans, gross Loans Gross, Before Allowance For Credit Loss Loans Gross, Before Allowance For Credit Loss % of Total Class of Financing Receivable Loan Modifications Made to Borrowers Experiencing Financial Difficulty, Percentage Loan Modifications Made to Borrowers Experiencing Financial Difficulty, Percentage 2026 Share Repurchase Program 2026 Share Repurchase Program [Member] 2026 Share Repurchase Program Fair Value Measurement Inputs and Valuation Techniques [Line Items] Fair Value Measurement Inputs and Valuation Techniques [Line Items] Total investments Investments Tier 1 Capital (to Risk-Weighted Assets) Banking Regulation, Tier 1 Risk-Based Capital Ratio, Actual Percentage of Private Education Loans in repayment, Year 4 Percentage Of Loans In Repayment, Originated Three Years Before Latest Fiscal Year Percentage Of Loans In Repayment, Originated Three Years Before Latest Fiscal Year Subsequent Event Type [Domain] Subsequent Event Type [Domain] Loans in forbearance as a percentage of loans in repayment and forbearance, Year 3 Loans In Forbearance As A Percentage Of Private Education Loans In repayment And Forbearance, Originated Two Years Before Current Fiscal Year Loans In Forbearance As A Percentage Of Private Education Loans In repayment And Forbearance, Originated Two Years Before Current Fiscal Year Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Loans in forbearance as a percentage of loans in repayment and forbearance Loans In Forbearance As A Percentage Of Private Education Loans In repayment And Forbearance Loans In Forbearance As A Percentage Of Private Education Loans In repayment And Forbearance Fair Value Measurement Inputs and Valuation Techniques Fair Value Measurement Inputs and Valuation Techniques [Table Text Block] Issuance costs Payments of Debt Issuance Costs Entity Current Reporting Status Entity Current Reporting Status Reportable Segment Reportable Segment [Member] Reportable Segment Total net cash used in financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Total Shareholder Return Amount Total Shareholder Return Amount Shares repurchased related to employee stock-based compensation plans Share-Based Payment Arrangement, Decrease for Tax Withholding Obligation Liabilities: Liabilities, Fair Value Disclosure [Abstract] Cash Flow Hedges Cash Flow Cash Flow Hedging [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] Total Private Education Loans in forbearance, After Year 5 Financing Receivable, Loans In Forbearance, Year Six, Originated, More Than Six Years before Current Fiscal Year Financing Receivable, Loans In Forbearance, Year Six, Originated, More Than Six Years before Current Fiscal Year Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Total Private Education Loans, Year 3 Loans, Originated Two Years Before Current Fiscal Year Loans, Originated Two Years Before Current Fiscal Year Transfer to allowance for loan losses Transfer - funded loans Off-Balance Sheet, Credit Loss, Liability, Writeoff Off-Balance Sheet, Credit Loss, Liability, Writeoff Percentage of Private Education Loans in repayment, Year 1 Percentage Of Loans In Repayment, Originated In Current Fiscal Year Percentage Of Loans In Repayment, Originated In Current Fiscal Year Adjustments to reconcile net income to net cash used in operating activities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Financing receivable, modified in period, subsequently charged off, amount Financing Receivable, Modified in Period, Subsequently Charged Off, Amount Financing Receivable, Modified in Period, Subsequently Charged Off, Amount Total Private Education Loans in Repayment, Year 1 Loans In Repayment, Originated In Current Fiscal Year Total loans in repayment. Financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Premises and equipment, net Property, Plant, and Equipment, after Accumulated Depreciation, Depletion, and Amortization Financial Instruments [Domain] Financial Instruments [Domain] Year 5 Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year Derivative assets Derivative values with impact of master netting agreements (as carried on balance sheet) Derivative instruments Derivative Asset Number of central counterparties Number Of Counterparties Number Of Counterparties Intangible Asset, Finite-Lived, Class [Axis] Intangible Asset, Finite-Lived, Class [Axis] 2026 Maturity 2026 [Member] Maturity 2026 Goodwill and Acquired Intangible Assets Intangible Asset and Goodwill [Text Block] Underlying Securities Award Underlying Securities Amount Fair Value Estimate of Fair Value Measurement [Member] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Combination - Interest Rate Reduction and Term Extension Extended Maturity and Interest Rate Reduction [Member] Derivative Asset, Statement of Financial Position [Extensible Enumeration] Derivative Asset, Statement of Financial Position [Extensible Enumeration] Preferred Stock Preferred Stock [Member] Total Private Education Loans, gross, Year 5 Loans Gross, Originated Four Years Before Latest Fiscal Year Loans Gross, Originated Four Years Before Latest Fiscal Year Segment Reporting [Table] Segment Reporting [Table] Unrealized (losses) gains on investments OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment, before Tax Private Education Loans allowance for losses, Year 5 Financing Receivable, Allowance For Credit Loss, Originated Four Years Before Current Fiscal Year Financing Receivable, Allowance For Credit Loss, Originated Four Years Before Current Fiscal Year Beginning balance Ending balance Total Exposure Off-Balance-Sheet, Credit Loss, Liability Schedule of Amortized Cost and Fair Value of Securities Available-for-Sale Schedule of Available-for-Sale Securities Reconciliation [Table Text Block] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] All Trading Arrangements All Trading Arrangements [Member] Estimated Fair Value Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months Other Performance Measure, Amount Other Performance Measure, Amount Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Delinquent Private Education Loans in repayment as a percentage of Private Education Loans in repayment, Year 4 Delinquencies As Percentage Of Loans In Repayment, Originated Three Years Before Current Fiscal Year Delinquencies As Percentage Of Loans In Repayment, Originated Three Years Before Current Fiscal Year Current Fiscal Year End Date Current Fiscal Year End Date Monthly payment that is smaller than the interest accrued on the loan in that month Fixed-Pay Loan, Monthly Payment Amount, Below Monthly Accrued Interest Fixed-Pay Loan, Monthly Payment Amount, Below Monthly Accrued Interest Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Provision for current period Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal) Derivative [Line Items] Derivative [Line Items] Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Declared dividends per common share (in dollars per share) Common stock dividend (in dollars per share) Common Stock, Dividends, Per Share, Declared Entity File Number Entity File Number Accrued interest receivable expected to be capitalized reserved Accrued Interest Receivable Expected To Be Capitalized Reserved Allowance For Credit Losses Accrued Interest Receivable Expected To Be Capitalized Reserved Allowance For Credit Losses Schedule of Amortized Cost and Fair Value of Securities by Contractual Maturities Investments Classified by Contractual Maturity Date [Table Text Block] Less: amount of gain (loss) reclassified in interest expense Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax Debt Securities Debt Securities, Available-for-Sale, Measurement Input Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Measure: Measure [Axis] Schedule of Variable Interest Entities Schedule of Variable Interest Entities [Table Text Block] Cash and cash equivalents Cash And Investments Interest Income Loss Cash and investments interest income (loss). After three to four years Time Deposit Maturities, Rolling Year Four Common stock held in treasury (in shares) Beginning balance (in shares) Ending balance (in shares) Treasury Stock, Common, Shares Tax benefit on accumulated other comprehensive loss AOCI Tax, Attributable to Parent Total adjustments Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity Equity Components [Axis] Equity Components [Axis] Fair value of repurchased amount Debt Instrument, Repurchase Amount 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 Private Education Loans deferred origination costs and unamortized premium/(discount), Year 5 Net Unamortized Premium Or Discount, Originated Four Years Before Current Fiscal Year Net Unamortized Premium Or Discount, Originated Four Years Before Current Fiscal Year Entity Interactive Data Current Entity Interactive Data Current Tier 1 Capital (to Average Assets) Banking Regulation, Tier 1 Leverage Capital, Well Capitalized, Minimum Entity Small Business Entity Small Business Current period recoveries, Year 4 Financing Receivable, Allowance for Credit Loss, Recovery, Originated Three Years Before Current Fiscal Year Financing Receivable, Allowance for Credit Loss, Recovery, Originated Three Years Before Current Fiscal Year Total comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive Income (Loss), Net of Tax, Attributable to Parent Shares repurchased related to employee stock-based compensation plans (in shares) Shares repurchased related to employee stock-based compensation plans (in shares) Share-Based Payment Arrangement, Shares Withheld for Tax Withholding Obligation Tier 1 Capital (to Average Assets) Banking Regulation, Tier 1 Leverage Capital Ratio, Well Capitalized, Minimum Weighted average useful life of acquired intangible assets Intangible Asset, Finite-Lived, Acquired, Weighted-Average Amortization Period After two to three years Time Deposit Maturities, Rolling Year Three 2045 Maturity 2045 [Member] Maturity 2045 [Member] Loans in forbearance as a percentage of loans in repayment and forbearance, After Year 5 Loans In Forbearance As A Percentage Of Private Education Loans In repayment And Forbearance Originated Five Or More Years Before Current Fiscal Year Loans In Forbearance As A Percentage Of Private Education Loans In repayment And Forbearance Originated Five Or More Years Before Current Fiscal Year Senior Unsecured Notes Due October 29, 2025 Senior Unsecured Notes Due October 29, 2025 [Member] Senior Unsecured Notes Due October 29, 2025 Loans in forbearance as a percentage of loans in repayment and forbearance, Year 2 Loans In Forbearance As A Percentage Of Private Education Loans In repayment And Forbearance, Originated In Fiscal Year Before Latest Fiscal Year Loans In Forbearance As A Percentage Of Private Education Loans In repayment And Forbearance, Originated In Fiscal Year Before Latest Fiscal Year Net interest income Interest Income (Expense), Operating MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Document Type Document Type Repurchase principal amount Debt Instrument, Repurchased Face Amount 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] Gain (loss) on extinguishment of debt Gain (Loss) on Extinguishment of Debt Unfunded Commitments Unfunded Commitments [Abstract] Unfunded Commitments Significant Accounting Policies Significant Accounting Policies [Text Block] Tier 1 Capital (to Average Assets) Banking Regulation, Tier 1 Leverage Capital Ratio, Actual Subsequent Event [Line Items] Subsequent Event [Line Items] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Local Phone Number Local Phone Number Fair Value Hedges Effect of Fair Value Hedges on Results of Operations [Abstract] Changes in operating assets and liabilities: Increase (Decrease) in Operating Assets [Abstract] Loans in forbearance as a percentage of loans in repayment and forbearance, Year 5 Loans In Forbearance As A Percentage Of Private Education Loans In repayment And Forbearance, Originated Four Years Before Current Fiscal Year Loans In Forbearance As A Percentage Of Private Education Loans In repayment And Forbearance, Originated Four Years Before Current Fiscal Year Income before income tax expense Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Commitments and contingencies Commitments and Contingencies Borrowings collateralized by loans in securitization trusts - issued Borrowings Collateralized By Loans In Trust Issued Borrowings Collateralized By Loans In Trust Issued Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Axis] Executive Category: Executive Category [Axis] LCH London Clearing House [Member] London Clearing House [Member] Income tax (expense) benefit Other Comprehensive Income (Loss), Tax Other Commitments [Table] Other Commitments [Table] 2047 Maturity 2047 [Member] Maturity 2047 [Member] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount 2026-A ABS Transaction SMB Private Education Loan Trust 2026-A [Member] SMB Private Education Loan Trust 2026-A Gains (losses) on sales of loans, net Gains on sales of loans, net Gain (Loss) on Sales of Loans, Net Financing receivable allowance period increase (decrease) Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease) Cash disbursements made for: Supplemental Cash Flow Information [Abstract] Fees paid on Secured Borrowing Facility Net Increase (Decrease) In Upfront Loan Fees Net Increase (Decrease) In Upfront Loan Fees PEO Name PEO Name Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] Interest-bearing liabilities: Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Seasoning based on monthly scheduled payments due from 1-12 payments 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. Income taxes paid Income Tax Paid, before Refund Received Certificates of deposit Interest-Bearing Domestic Deposit, Time Deposits Amount Interest-Bearing Deposit Liabilities, Domestic, by Component [Abstract] Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Entity Tax Identification Number Entity Tax Identification Number Age Analysis of Past Due Loans Delinquencies Financing Receivable, Past Due [Table Text Block] U.S. Basel III Minimum Requirements Plus Buffer, Ratio Banking Regulation, Leverage Ratio [Abstract] Loan delinquent, current Financial Asset, Not Past Due [Member] Unrealized losses on cash flow hedges Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax Other Commitments [Line Items] Other Commitments [Line Items] Preferred stock dividends Preferred Stock Dividends, Income Statement Impact Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Measurement Frequency [Domain] Measurement Frequency [Domain] Debt Instrument [Axis] Debt Instrument [Axis] Subsequent Event Table Subsequent Event [Table] Savings Interest-Bearing Domestic Deposit, Savings Stock-based compensation expense Share-Based Payment Arrangement, Noncash Expense Interest expense: Interest Expense, Operating and Nonoperating [Abstract] Compensation and benefits Labor and Related Expense Credit Score, FICO [Domain] Credit Score, FICO [Domain] 2044 Maturity 2044 [Member] Maturity 2044 [Member] Schedule of Impact of Derivatives on the Consolidated Balance Sheet Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Basic earnings per common share (in dollars per share) Basic earnings per common share (in dollars per share) Earnings Per Share, Basic Measurement Input Type [Axis] Measurement Input Type [Axis] Current period recoveries, Year 3 Financing Receivable, Allowance for Credit Loss, Recovery, Originated Two Years Before Current Fiscal Year Financing Receivable, Allowance for Credit Loss, Recovery, Originated Two Years Before Current Fiscal Year Private Education Loans allowance for losses, Year 2 Financing Receivable, Allowance For Credit Loss, Originated Fiscal Year Before Latest Fiscal Year Financing Receivable, Allowance For Credit Loss, Originated Fiscal Year Before Latest Fiscal Year Insider Trading Arrangements [Line Items] Short-term borrowings Short-Term Debt, Fair Value Total Private Education Loans in forbearance, Year 2 Financing Receivable, Loans In Forbearance, Year Two, Originated, Fiscal Year before Current Fiscal Year Financing Receivable, Loans In Forbearance, Year Two, Originated, Fiscal Year before Current Fiscal Year Delinquent Private Education Loans in repayment as a percentage of Private Education Loans in repayment, Year 1 Delinquencies As Percentage Of Loans In Repayment, Originated In Current Fiscal Year Delinquencies As Percentage Of Loans In Repayment, Originated In Current Fiscal Year Schedule of Common Share Repurchases Class of Treasury Stock [Table Text Block] Average purchase price per share (in dollars per share) Treasury Stock Acquired, Average Cost Per Share, Including Commission Costs Treasury Stock Acquired, Average Cost Per Share, Including Commission Costs Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Private Education Loans deferred origination costs and unamortized premium/(discount), Year 4 Net Unamortized Premium Or Discount, Originated Three Years Before Current Fiscal Year Net Unamortized Premium Or Discount, Originated Three Years Before Current Fiscal Year Fair Value Measurement [Domain] Fair Value Measurement [Domain] Recoveries Current period recoveries, total Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Recovery Loans In-school/grace/deferment Loans In-School/Grace/Deferment [Member] Loans In-School/Grace/Deferment Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] 2043 Maturity 2043 [Member] Maturity 2043 [Member] Cover page. Cover [Abstract] Fair Value Measurement Inputs and Valuation Techniques [Table] Fair Value Measurement Inputs and Valuation Techniques [Table] Total Private Education Loans in forbearance, Year 5 Financing Receivable, Loans In Forbearance, Year Five, Originated, Four Years before Current Fiscal Year Financing Receivable, Loans In Forbearance, Year Five, Originated, Four Years before Current Fiscal Year Equity Awards Adjustments Equity Awards Adjustments [Member] Hedging Relationship [Domain] Hedging Relationship [Domain] Ending total loans, gross Allowance Coverage Of Charge Offs Ending Loans Allowance coverage of charge-offs ending total loans. Measurement Input, Prepayment Rate Measurement Input, Prepayment Rate [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Increase (decrease) in other liabilities Increase (Decrease) in Other Operating Liabilities Schedule of Loans Held for Investment Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Percent of debt fair value Debt Instrument, Repurchase Price, Percentage Debt Instrument, Repurchase Price, Percentage Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Other securities Other Debt Obligations [Member] Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Assets/(Liabilities) Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease) Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Loans Transferred to the Trust Debt Instrument, Loans Transferred Debt Instrument, Loans Transferred Common Equity Tier 1 Capital (to Risk-Weighted Assets) Common Equity Tier One Risk Based Capital Common Equity Tier One Risk Based Capital Loans in forbearance as a percentage of loans in repayment and forbearance, Year 1 Loans In Forbearance As Percentage Of Loans In Repayment And Forbearance Loans in forbearance as a percentage of loans in repayment and forbearance. Increments in which forbearance is granted Financing Receivable, Increments In Which Forbearance Is Granted Financing Receivable, Increments In Which Forbearance Is Granted Share Repurchase Program [Axis] Share Repurchase Program [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Class of Stock [Domain] Class of Stock [Domain] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Investments Interest Income, Debt Securities, Available-for-Sale, Operating Other adjustments to net income, net Other Noncash Income (Expense) 2042 Maturity 2042 [Member] Maturity 2042 [Member] Current period recoveries, Year 1 Financing Receivable, Allowance for Credit Loss, Recovery, Originated In Current Fiscal Year Financing Receivable, Allowance for Credit Loss, Recovery, Originated In Current Fiscal Year Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Loans held for investment, net, difference Loans Receivable, Fair Value Disclosure, Difference Between Carrying Value And Fair Value Loans Receivable, Fair Value Disclosure, Difference Weighted Average Life of Notes (in years) Debt Instrument, Weighted Average Life Debt Instrument, Weighted Average Life Low income housing tax credit investments, tax credits and benefits (less than) Investment Program, Proportional Amortization Method, Elected, Income Tax Credit and Other Income Tax Benefit, before Amortization Expense Entity Filer Category Entity Filer Category Estimated Fair Value Debt Securities, Available-for-Sale, Unrealized Loss Position Carrying Amount of Net Assets Securing Debt Outstanding Variable Interest Entity, Nonconsolidated, Comparison of Carrying Amount of Assets and Liabilities to Maximum Loss Exposure [Abstract] Schedule of Offsetting Liabilities Offsetting Liabilities [Table Text Block] Retail and other deposits Retail And Other Deposits Retail And Other Deposits Current period gross charge-offs, Year 1 Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Writeoff, Originated In Current Fiscal Year Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Writeoff, Originated In Current Fiscal Year Financial Asset, Period Past Due [Axis] Financial Asset, Aging [Axis] Private Education Loans, net, After Year 5 Financing Receivable, after Allowance for Credit Loss, Originated Five Years Before Current Fiscal Year Financing Receivable, after Allowance for Credit Loss, Originated Five Years Before Current Fiscal Year Investments, Debt and Equity Securities [Abstract] Investments, Debt and Equity Securities [Abstract] Percentage of Private Education Loans in repayment, After Year 5 Percentage Of Loans In Repayment, Originated Five Or More Years Before Latest Fiscal Year Percentage Of Loans In Repayment, Originated Five Or More Years Before Latest Fiscal Year Total SLM Corporation stockholders’ equity before treasury stock Stockholders' Equity Attributable To Parent, Excluding Treasury Stock Stockholders' Equity Attributable To Parent, Excluding Treasury Stock Change in unrealized gains or losses for the period included in earnings (or changes in net assets) for assets held at the end of the reporting period Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss) Debt instrument, issuance price, percentage Debt Instrument, Issuance Price, Percentage Debt Instrument, Issuance Price, Percentage Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Schedule of Stock by Class [Table] Stock, Class of Stock [Table] Derivative liabilities Derivative values with impact of master netting agreements (as carried on balance sheet) Derivative instruments Derivative instruments Derivative Liability Entity Address, Address Line One Entity Address, Address Line One Percent of private loans indexed to LIBOR Percent of Private Loans indexed to LIBOR Or SOFR Percent of Private Loans indexed to LIBOR Or SOFR Total accrued interest by origination vintage, After Year 5 Financing Receivable, Accrued Interest, Origination Interest, Originated Five or More Years before Latest Fiscal Year Financing Receivable, Accrued Interest, Origination Interest, Originated Five or More Years before Latest Fiscal Year Income tax expense Income Tax Expense (Benefit) Fair Value Hedges Fair Value Fair Value Hedging [Member] 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 Restricted cash Restricted Cash Restricted Cash and Investments Consolidation Consolidation, Policy [Policy Text Block] Charge-offs Current period gross charge-offs, total Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff Private Education Loans allowance for losses, Year 4 Financing Receivable, Allowance For Credit Loss, Originated Three Years Before Current Fiscal Year Financing Receivable, Allowance For Credit Loss, Originated Three Years Before Current Fiscal Year Variable Interest Entity, Primary Beneficiary Variable Interest Entity, Primary Beneficiary [Member] Loan Restructuring Modification [Domain] Loan Restructuring Modification [Domain] Valuation Technique, Discounted Cash Flow Valuation Technique, Discounted Cash Flow [Member] Statement [Table] Statement [Table] One year or less Time Deposit Maturities, Next Rolling 12 Months U.S. government-sponsored enterprises and Treasuries U.S. Government-Sponsored Enterprises and Treasuries [Member] U.S. Government-Sponsored Enterprises and Treasuries Current period gross charge-offs, After Year 5 Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Writeoff, Originated Five Or More Years Before Latest Fiscal Year Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Writeoff, Originated Five Or More Years Before Latest Fiscal Year Tier 1 Capital (to Risk-Weighted Assets) Banking Regulation, Tier 1 Risk-Based Capital Ratio, Well Capitalized, Minimum Secured Borrowing Facility ABCP borrowings ABCP Borrowings [Member] ABCP Borrowings [Member] Unfunded loan commitments sold Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability, Unfunded Loan Commitments Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability, Unfunded Loan Commitments Certificates of deposit Certificates of Deposit [Member] Year 2 Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year Private Education Loans deferred origination costs and unamortized premium/(discount), Year 3 Net Unamortized Premium Or Discount, Originated Two Years Before Current Fiscal Year Net Unamortized Premium Or Discount, Originated Two Years Before Current Fiscal Year Amount of variation margin included as settlement Amount Of Variation Margin Included As Settlement Amount Of Variation Margin Included As Settlement Gross position Derivative Asset, Subject to Master Netting Arrangement, before Offset Held for sale loans Loan, Held-for-Sale, Fair Value Disclosure Weighted Average Cost of Funds (as a percent) Derivative, Basis Spread on Variable Rate Additional Loans the Bank Transferred to the Trust Additional Proceeds From Sale Of Debt Securities, Available-For-Sale Additional Proceeds From Sale Of Debt Securities, Available-For-Sale Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract]