Liability for unfunded commitments Investment Program, Proportional Amortization Method, Elected, Commitment Banking and Thrift, Other Disclosure [Abstract] Banking and Thrift, Other Disclosure [Abstract] Adjustments to reconcile net income to net cash provided by (used in) operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Remaining authority under the share repurchase program Share Repurchase Program, Remaining Authorized, Amount 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] Collateral [Domain] Collateral Held [Domain] Cover page. Cover [Abstract] 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] Net increase (decrease) in cash, cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Gains (losses) on sales of loans, net Gains on sales of loans, net Gain (Loss) on Sales of Loans, Net Temporary interest rate reduction, period Financing Receivable, Temporary Interest Rate Reduction, Period Financing Receivable, Temporary Interest Rate Reduction, Period 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) Hedged items recorded in interest expense Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge Trading Symbol Trading Symbol Fair Value Hedges Fair Value Fair Value Hedging [Member] Money market Interest-Bearing Domestic Deposit, Money Market Weighted average life of loans Weighted Average Life of Loans Weighted Average Life of Loans Total comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Gross position Derivative Asset, Subject to Master Netting Arrangement, before Offset Non-NEOs Non-NEOs [Member] 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 Declared dividends per common share (in dollars per share) Common stock dividend (in dollars per share) Common Stock, Dividends, Per Share, Declared Loans held for sale Loans held for sale Financing Receivable, Held-for-Sale, Not Part of Disposal Group, after Valuation Allowance Allowance for Uncollectible Interest Allowance For Uncollectible Accrued Interest Allowance For Uncollectible Accrued Interest Line of Credit Facility [Table] Line of Credit Facility [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Borrowings collateralized by loans in securitization trusts - repaid Borrowings Collateralized By Loans In Trust Repaid Borrowings Collateralized By Loans In Trust Repaid Hedging Relationship [Domain] Hedging Relationship [Domain] 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 Fair Value Measurements Fair Value Disclosures [Text Block] Total unrealized gains (losses) Other Comprehensive Income (Loss), before Tax Award Timing Disclosures [Line Items] Financial Asset, Period Past Due [Axis] Financial Asset, Aging [Axis] Total Derivative, Gain (Loss) on Derivative, Net Schedule of Allowance for Credit Losses and Recorded Investments in Loans Financing Receivable, Allowance for Credit Loss [Table Text Block] Financing Receivable, Past Due [Table] Financing Receivable, Past Due [Table] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] (Decrease) increase in accrued interest payable Increase (Decrease) in Interest Payable, Net Net interest income Interest Income (Expense), Operating Total adjustments Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities Cost Basis Finite-Lived Intangible Assets, Gross After Year 5 Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year Total Private Education Loans, Year 2 Loans, Originated In Fiscal Year Before Latest Fiscal Year Loans, Originated In Fiscal Year Before Latest Fiscal Year Class of Financing Receivable [Domain] Class of Financing Receivable [Domain] Total net cash used in operating activities Net Cash Provided by (Used in) Operating Activities Residual Interests Debt Securities, Trading, Measurement Input Operating activities Net Cash Provided by (Used in) Operating Activities [Abstract] Schedule of Derivative Instruments, Effect on Other Comprehensive Income (Loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Secured Borrowings Secured Debt [Member] Net increase 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 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 Award Timing Method Award Timing Method [Text Block] Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Accrued interest receivable, difference Accrued Interest Receivable, Fair Value Disclosure, Difference Accrued Interest Receivable, Fair Value Disclosure, Difference Principal amount of collateral Loans Pledged As Collateral, Principal Amount Loans Pledged As Collateral, Principal Amount Measurement Frequency [Axis] Measurement Frequency [Axis] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Loans acquired and originated Student Loans Acquired And Originated Student Loans Acquired And Originated Insider Trading Policies and Procedures [Line Items] Charge-Offs Financing Receivable, Troubled Debt Restructuring, Write-Down Financing Receivable, Troubled Debt Restructuring, Write-Down Percentage amount deferred per year Adoption Of New Accounting Pronouncements, Percent Deferred Per Year Adoption Of New Accounting Pronouncements, Percent Deferred Per Year Adjustment to Compensation, Amount Adjustment to Compensation Amount Partner relationships Partner Relationships [Member] Partner Relationships Compensation Amount Outstanding Recovery Compensation Amount 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] Entity Small Business Entity Small Business Company Selected Measure Amount Company Selected Measure Amount Issuance costs for collateralized borrowings Payments of Debt Issuance Costs Tabular List, Table Tabular List [Table Text Block] Other impacts to the provisions for credit losses: Financing Receivable, Credit Loss, Expense (Reversal), Other Impacts Financing Receivable, Credit Loss, Expense (Reversal), Other Impacts 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 2023-A SMB Private Education Loan Trust 2023-A [Member] SMB Private Education Loan Trust 2023-A Level 3  Fair Value, Inputs, Level 3 [Member] Fair Value Measurement Inputs and Valuation Techniques [Table] Fair Value Measurement Inputs and Valuation Techniques [Table] Unrealized (gains) losses on derivatives and hedging activities, net Unrealized Gain (Loss) on Derivatives Antidilutive securities excluded from computation of earnings per share (less than) (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Non-interest expenses: Noninterest Expense [Abstract] Schedule of Interest Bearing Deposits Interest Bearing Deposits [Table Text Block] [Table Text Block] for Interest Bearing Deposits [Table] Financing receivable, modified in period, to total financing receivable, percentage Financing Receivable, Modified in Period, to Total Financing Receivables, Percentage 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 Accrued interest to be capitalized Accrued Interest to be Capitalized [Abstract] Accrued Interest to be Capitalized 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 Credit Facility [Domain] Credit Facility [Domain] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Accounts and Financing Receivables [Table] 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] 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. Goodwill Goodwill Deposits exceeding FDIC insurance limits Cash, Uninsured Amount 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 Aggregate purchase price (not to exceed) Share Repurchase Program, Authorized, Amount Income taxes refunded Proceeds from Income Tax Refunds 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 2025 Maturity 2025 [Member] Maturity 2025 Deposits - interest-bearing Deposits - interest bearing Interest-Bearing Deposit Liabilities Entity Information [Line Items] Entity Information [Line Items] Employee Stock Option Share-Based Payment Arrangement, Option [Member] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Axis] Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-Sale [Table] Depreciation of premises and equipment Depreciation 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. 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 Schedule of Amortized Cost and Fair Value of Securities by Contractual Maturities Investments Classified by Contractual Maturity Date [Table Text Block] Award Type Award Type [Axis] 2046 Maturity 2046 [Member] Maturity 2046 [Member] Adjustments Cumulative Effect, Period of Adoption, Adjustment [Member] 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 Premises and equipment, net Property, Plant and Equipment, Net Total liabilities Liabilities Common stock dividend (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Weighted average useful life of acquired intangible assets Acquired Finite-Lived Intangible Assets, Weighted Average Useful Life Expiration Date Trading Arrangement Expiration Date Investing activities Net Cash Provided by (Used in) Investing Activities [Abstract] Other income Noninterest Income, Other Operating Income Seasoning Repayments [Member] Repayments credit quality indicators that are developed and used internally by the company. Total Shareholder Return Amount Total Shareholder Return Amount Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Transfers out of level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 Financial Asset, Period Past Due [Domain] Financial Asset, Aging [Domain] Utah Housing Corporation bonds Utah Housing Corporation Bonds [Member] Utah Housing Corporation Bonds [Member] Gain on sale Debt Securities, Available-for-Sale, Realized Gain Schedule of Common Share Repurchases Class of Treasury Stock [Table Text Block] Subsequent Event [Line Items] Subsequent Event [Line Items] Proceeds from sale of loans receivable Proceeds from Sale of Finance Receivables 90 Days or Greater Past Due Greater Than Ninety Days Past Due Accrued Interest Receivable Greater than ninety days past due accrued interest receivable. Amount of gain (loss) recognized in other comprehensive income (loss) Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax Debt Instrument [Line Items] Debt Instrument [Line Items] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Other assets Other Assets Other Assets 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 Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Tier 1 of government guarantee (at least) Tier One of Government Guarantee Tier One of Government Guarantee 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 Provisions for unfunded loan commitments Financing Receivable, Credit Loss, Expense (Reversal), Existing Commitments Financing Receivable, Credit Loss, Expense (Reversal), Existing Commitments Measurement Input, Default Rate Measurement Input, Default Rate [Member] Total Private Education Loans, Year 5 Loans, Originated Four Years Before Latest Fiscal Year Loans, Originated Four Years Before Latest Fiscal Year Accrued interest payable Accrued Liabilities, Fair Value Disclosure MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Rule 10b5-1 Trading Plan Rule 10b5-1 Trading Plan [Member] Rule 10b5-1 Trading Plan Preferred stock dividend rate (in dollars per share) Preferred Stock, Dividend Rate, Per-Dollar-Amount Actual Amount Banking Regulation, Total Capital [Abstract] 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 Loan delinquent, 60 days Financial Asset, Equal to 60 Days Past Due [Member] Financial Asset, Equal to 60 Days Past Due Year 1 Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year Document Fiscal Period Focus Document Fiscal Period Focus All Executive Categories All Executive Categories [Member] 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 Securities Financing Transaction [Table] Security Financing Transaction [Table] One year or less Time Deposit Maturities, Next Rolling 12 Months Expected amortization of 2025 Finite-Lived Intangible Asset, Expected Amortization, Year Two 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 Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Assets Assets [Abstract] Net charge-offs Current period net charge-offs, total Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff (Recovery) Other comprehensive income (loss), net of tax (expense) benefit Other comprehensive loss, net of tax Other Comprehensive Income (Loss), Net of Tax Document Type Document Type Derivative Contract [Domain] Derivative Contract [Domain] Private education loans Percent Of Private Loans Percent of private loans Gains (losses) on securities, net Gain (Loss) on Investments [Member] Derivative Liability, Statement of Financial Position [Extensible Enumeration] Derivative Liability, Statement of Financial Position [Extensible Enumeration] Available-for sale investments at fair value, cost Amortized Cost Debt Securities, Available-for-Sale, Amortized Cost 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 Subsequent Event Table Subsequent Event [Table] Loan delinquent 60-89 days 60-89 Days Past Due Financial Asset, 60 to 89 Days Past Due [Member] Maximum Maximum [Member] 12 months or more Debt Securities, Available-for-Sale [Abstract] Series B: 2.5 million and 2.5 million shares issued, respectively, at stated value of $100 per share Preferred Stock, Value, Outstanding 2022 Share Repurchase Program 2022 Share Repurchase Program [Member] 2022 Share Repurchase Program Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Net Finite-Lived Intangible Assets, Net Investment Type [Axis] Investment Type [Axis] Schedule of Offsetting Liabilities Offsetting Liabilities [Table Text Block] Period of deferment Period Of Deferment For Adoption Of New Accounting Pronouncements Period Of Deferment For Adoption Of New Accounting Pronouncements 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 Statistical Measurement [Axis] Statistical Measurement [Axis] Weighted Average Interest Rate Weighted Average Interest Rate On Loans Weighted Average Interest Rate On Loans Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Other liabilities reserve Other Liabilities Reserve Other Liabilities Reserve Income (loss) before income tax expense (benefit) Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Other comprehensive income (loss): Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract] Name Outstanding Recovery, Individual Name Net proceeds from sales of loans held for investment, principal Net Proceeds From Sales Of Student Loans Held For Sale, Principal Net Proceeds From Sales Of Student Loans Held For Sale, Principal 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 Award Timing Predetermined Award Timing Predetermined [Flag] 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 Gains (losses) on securities, net Gains on securities, net Gain (Loss) on Sales of Mortgage-Backed Securities (MBS) Subsequent Event Type [Domain] Subsequent Event Type [Domain] Common stock dividends paid Payments of Ordinary Dividends, Common Stock Financing receivable, excluding accrued interest, modified, subsequent default, unpaid principal balance Financing Receivable, Excluding Accrued Interest, Modified, Subsequent Default, Unpaid Principal Balance Financing Receivable, Excluding Accrued Interest, Modified, Subsequent Default, Unpaid Principal Balance 2058 Maturity 2058 [Member] Maturity 2058 Customer relationships Customer Relationships [Member] Diluted earnings per common share (in dollars per share) Earnings Per Share, Diluted Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Schedule of Accrued Interest Receivable Accrued Interest Receivable [Table Text Block] Accrued interest receivable. Amortization of deferred loan origination costs and loan premium/(discounts), net Amortization of Deferred Loan Origination Fees, Net Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Uncommitted federal funds Uncommitted Federal Funds Uncommitted Federal Funds Less: provisions for credit losses Provisions for credit losses Provisions for credit losses reported in consolidated statements of operations 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) Included in earnings (or changes in net assets) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Net income (loss) Net income (loss) Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Amortization of brokered deposit placement fee Amortization Of Brokered Deposit Placement amortization of brokered deposit placement Income tax expense (benefit) Income Tax Expense (Benefit) Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] 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 Notional value Notional Values Derivative, Notional Amount Derivative assets Derivative values with impact of master netting agreements (as carried on balance sheet) Derivative instruments Derivative Asset Certificates of deposit Weighted Average Rate Domestic Deposit, Time Deposits Financing Receivable Portfolio Segment [Domain] Financing Receivable Portfolio Segment [Domain] Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Interest expense: Interest Expense, Operating and Nonoperating [Abstract] Total net cash provided by (used in) investing activities Net Cash Provided by (Used in) Investing Activities Amount of gain (loss) reclassified from accumulated other comprehensive income into interest expense Interest Expense, Operating and Nonoperating 2024-R1 SMB Private Education Loan Trust 2024-R1 [Member] SMB Private Education Loan Trust 2024-R1 Deposits Deposits, Fair Value Disclosure U.S. Basel III Regulatory Requirements, Ratio Banking Regulation, Leverage Ratio [Abstract] Greater than or equal to 750 FICO score greater than 750 [Member] FICO score greater than 750 [Member] All Adjustments to Compensation All Adjustments to Compensation [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 Additional paid-in capital Additional Paid in Capital Short-Term Debt, Type [Domain] Short-Term Debt, Type [Domain] Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) [Table] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Carrying Amount of the Hedged Assets/(Liabilities) Hedged Liability, Fair Value Hedge 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 Equity Interests Debt Securities, Trading, and Equity Securities, FV-NI Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] With cosigner With Cosigner [Member] With Cosigner [Member] Ending balance: collectively evaluated for impairment Accrued Interest to be Capitalized, Collectively Evaluated for Impairment Accrued Interest to be Capitalized, Collectively Evaluated for Impairment Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Entity Address, State or Province Entity Address, State or Province Combination - Interest Rate Reduction and Term Extension Interest Rate Reduction And Term Extension [Member] Interest Rate Reduction And Term Extension Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract] Year 4 Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 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 Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] 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 2024 Share Repurchase Program 2024 Share Repurchase Program [Member] 2024 Share Repurchase Program Financial Instruments [Domain] Financial Instruments [Domain] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] 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 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 Net charge-offs: Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery [Abstract] 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 Restatement Determination Date Restatement Determination Date Fair Value Estimate of Fair Value Measurement [Member] Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Schedule of Amortized Cost and Fair Value of Securities Available-for-Sale Schedule of Available-for-Sale Securities Reconciliation [Table Text Block] Schedule of Securities Financing Transactions Schedule of Securities Financing Transactions [Table Text Block] Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Short-Term Debt, Type [Axis] Short-Term Debt, Type [Axis] Total interest-bearing liabilities Financial Liabilities Fair Value Disclosure Earnings (Loss) per Common Share Earnings Per Share [Text Block] 2039 Maturity 2039 [Member] Maturity 2039 [Member] Subsequent Event Subsequent Event [Member] Unrealized gains (losses) on cash flow hedges Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Other securities Other Debt Obligations [Member] Income tax (expense) benefit Other Comprehensive Income (Loss), Tax 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 Estimated weighted average life of student loans Estimated Weighted Average Life Of Student Loans Estimated weighted average life of student loans. Provisions for loan losses Financing Receivable, Credit Loss, Expense (Reversal), New Commitments Financing Receivable, Credit Loss, Expense (Reversal), New Commitments Cash Flow Hedges Effect of Cash Flow Hedges on Results of Operations [Abstract] Tradename and trademarks Trademarks and Trade Names [Member] 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 PEO PEO [Member] Name Trading Arrangement, Individual Name Deposits Interest Expense, Deposits Loans Carrying Amount Of Assets Securing Debt Outstanding Loans Carrying Amount Of Assets Securing Debt Outstanding Loans Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] 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 Other operating expenses Other Noninterest Expense Total Capital (to Risk-Weighted Assets) Banking Regulation, Total Risk-Based Capital, Well Capitalized, Minimum 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 Securities Financing Transaction [Line Items] Securities Financing Transaction [Line Items] Less: Common stock held in treasury at cost: 228.2 million and 217.9 million shares, respectively Treasury Stock, Common, Value Interest recognized on derivatives Gain (Loss) on Fair Value Hedges Recognized in Earnings Loans Interest and Fee Income, Loans and Leases Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Savings Weighted Average Rate Domestic Deposit, Savings FFELP Loans FFELP Loans(1) Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member] Interest rate offered to borrowers facing financial difficulty Financing Receivable, Temporary Interest Rate Reduction, Financial Difficulty Status Financing Receivable, Temporary Interest Rate Reduction, Financial Difficulty Status 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] Cash and cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Threshold period for payment default Financing Receivable, Threshold Period For Payment Default Financing Receivable, Threshold Period For Payment Default Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Local Phone Number Local Phone Number Total Debt, Long-Term and Short-Term, Combined Amount Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] 2055 Maturity 2055 [Member] Maturity 2055 Purchase of subsidiary, net of cash acquired Payments to Acquire Interest in Subsidiaries and Affiliates Provision for current period Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal) Year 5 Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year Allowance for credit losses Debt Securities, Available-for-Sale, Allowance for Credit Loss Unfunded Loan Commitments Credit Loss, Financial Instrument [Text Block] 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) PEO Total Compensation Amount PEO Total Compensation Amount Interest Income - Investments Interest Income [Member] Gross position Derivative Liability, Subject to Master Netting Arrangement, before Offset 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] Statement of Income Location, Balance [Axis] Statement of Income Location, Balance [Axis] Accrued interest on deposits Interest Payable, Current Total Capital (to Risk-Weighted Assets) Banking Regulation, Total Risk-Based Capital Ratio, Actual 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 Debt Disclosure [Abstract] Debt Disclosure [Abstract] 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 Common Stock Common Stock [Member] 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. Total Capital (to Risk-Weighted Assets) Banking Regulation, Total Capital, Actual Cash collateral pledged Derivative Liability, Subject to Master Netting Arrangement, Collateral, Right to Reclaim Cash Not Offset Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Scholly, Inc. Scholly, Inc. [Member] Scholly, Inc. Gain on sales of loans, net Gain (loss) on sale of financing receivable Gain (Loss) on Sale of Financing Receivable Qtr.-End Weighted Average Stated Rate Weighted Average Rate Domestic Deposit Liabilities [Abstract] Line of Credit Line of Credit [Member] 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 Entity Central Index Key Entity Central Index Key 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 Credit Score, FICO [Axis] Credit Score, FICO [Axis] Financing Receivable, Allowance for Credit Loss [Roll Forward] Financing Receivable, Allowance for Credit Loss [Roll Forward] Loan Deferment Loan Deferment [Member] Loan Deferment Beginning balance Ending balance Total Exposure Liability for unfunded commitments Off-Balance-Sheet, Credit Loss, Liability Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount 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] Stockholders' Equity Equity [Text Block] Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Financial Instrument [Axis] Financial Instrument [Axis] 2053 Maturity 2053 [Member] Maturity 2053 2050 Maturity 2050 [Member] Maturity 2050 Money market Weighted Average Rate Domestic Deposit, Money Market Stock-based compensation expense APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Loans Loans [Abstract] Loans. Measurement Basis [Axis] Measurement Basis [Axis] Loans held for investment, net Loans Receivable, Fair Value Disclosure Title Trading Arrangement, Individual Title Consolidated Entities [Axis] Consolidated Entities [Axis] Unsecured borrowings Unsecured Debt [Member] Lendable value of collateral Lendable Value Of Collateral Lendable Value Of Collateral City Area Code City Area Code Total Private Education Loans, Year 4 Loans, Originated Three Years Before Latest Fiscal Year Loans, Originated Three Years Before Latest Fiscal Year Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Investments Interest Income, Debt Securities, Available-for-Sale, Operating Preferred Stock Preferred Stock [Member] Charge-offs Current period gross charge-offs, total Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff Common stock repurchased Payments for Repurchase of Common Stock Brokered deposit placement fee Brokered Deposit Placement Fee Brokered Deposit Placement Fee 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] Fair Value Measurement Inputs and Valuation Techniques Fair Value Measurement Inputs and Valuation Techniques [Table Text Block] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Unsecured debt issued Proceeds from Issuance of Unsecured Debt After three years to four years Time Deposit Maturities, Rolling Year Four 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 Earnings Per Share [Abstract] Earnings Per Share [Abstract] Equity [Abstract] Equity [Abstract] Retained earnings Retained Earnings (Accumulated Deficit) Schedule of Compliance with Regulatory Capital Requirements Under Banking Regulations Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block] Class of Stock [Domain] Class of Stock [Domain] Estimated accumulated gain (loss) to be reclassified in next 12 months Cash Flow Hedge Gain (Loss) to be Reclassified within 12 Months 2051 Maturity 2051 [Member] Maturity 2051 Schedule of Debt Schedule of Debt [Table Text Block] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Equity Awards Adjustments Equity Awards Adjustments [Member] Fair Value Hedges Gain (Loss) on Fair Value Hedges Recognized in Earnings [Abstract] Underlying Securities Award Underlying Securities Amount Investments Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Common Stock Dividends, Common Stock, Cash Amendment Flag Amendment Flag Carrying Value Reported Value Measurement [Member] 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 Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Loans pledged as collateral Securities Loaned, Fair Value of Collateral Total Available-For-Sale Securities, Unrealized Loss Position [Abstract] Available-For-Sale Securities, Unrealized Loss Position [Abstract] Subsequent Events [Abstract] Recoveries Current period recoveries, total Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Recovery 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 Borrowings Debt Disclosure [Text Block] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] Collateral [Axis] Collateral Held [Axis] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Total Issued Debt Instrument, Face Amount Entity Address, Postal Zip Code Entity Address, Postal Zip Code Interest rate swaps Interest rate swaps Interest Rate Swap [Member] FICO at Origination School Fico [Member] School type fico credit quality indicators that are developed and used internally by the company. Tier 1 Capital (to Risk-Weighted Assets) Banking Regulation, Tier 1 Risk-Based Capital, Well Capitalized, Minimum Percentage amount phased in during year Adoption Of New Accounting Pronouncements, Percent Phased In During Year Adoption Of New Accounting Pronouncements, Percent Phased In During Year Tax benefit on accumulated other comprehensive loss AOCI Tax, Attributable to Parent Cash dividends declared: Dividends, Cash [Abstract] Cash and cash equivalents Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value FDIC assessment fees Federal Deposit Insurance Corporation Premium Expense 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. Certificates of deposit Certificates of Deposit [Member] 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] 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] Trading Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net [Abstract] Line of credit facility, interest holding percentage Line of Credit Facility, Interest Holding Percentage Line of Credit Facility, Interest Holding Percentage Variable Interest Entity, Not Primary Beneficiary Variable Interest Entity, Not Primary Beneficiary [Member] Trading Activity, by Type [Domain] Trading Activity, by Type [Domain] Fair Value Measurement [Domain] Fair Value Measurement [Domain] 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 Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Class of Financing Receivable [Axis] Class of Financing Receivable [Axis] Other Assets Derivative Asset [Abstract] Designated as Hedging Instrument Designated as Hedging Instrument [Member] Net income (loss) attributable to SLM Corporation common stock Net Income (Loss) Available to Common Stockholders, Basic Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] 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] Schedule of Stock by Class [Table] Stock, Class of Stock [Table] 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] Total assets Assets Other interest-earning assets Other Interest Earning Assets 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 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 unfunded commitment liability Off-Balance Sheet, Credit Loss, Liability, Transfer From Unfunded Commitments Off-Balance Sheet, Credit Loss, Liability, Transfer From Unfunded Commitments Modified Loans Financing receivable, modified in period, amount Financing Receivable, Modified in Period, Amount Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Cumulative Effect, Period Of Adoption [Axis] Cumulative Effect, Period of Adoption [Axis] Commitments and contingencies Commitments and Contingencies 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 Measurement Input, Prepayment Rate Measurement Input, Prepayment Rate [Member] Termination Date Trading Arrangement Termination Date 2038 Maturity 2038 [Member] Maturity 2038 [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Mortgage-backed securities Collateralized Mortgage-Backed Securities [Member] 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 Other liabilities Other Liabilities Net position Derivative Asset, Including Not Subject to Master Netting Arrangement, after Offset and Deduction Trading Trading Not Designated as Hedging Instrument [Member] Ownership interest percentage on asset-backed financing Loans Securitized or Asset Backed Financing Arrangement Ownership Interest Percentage Loans Securitized or Asset Backed Financing Arrangement Ownership Interest Percentage Debt Instrument [Axis] Debt Instrument [Axis] Private Education Loans Private Education Loans Private Education Loans [Member] Private education loans. Net income (loss) Net Income (Loss) Attributable to Parent Trading Arrangement: Trading Arrangement [Axis] Fair Values of Financial Assets and Liabilities, Including Derivative Financial Instruments Fair Value, by Balance Sheet Grouping [Table Text Block] Year 3 Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year Non-marketable securities investment Other Investment Not Readily Marketable, Fair Value Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Schedule of Offsetting Assets Offsetting Assets [Table Text Block] Average Balance Financing Receivable, Before Allowance For Credit Loss, Average Balance Financing Receivable, Before Allowance For Credit Loss, Average Balance Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Variable-rate Variable-rate Variable Income Interest Rate [Member] Entity File Number Entity File Number Consolidated Entities [Domain] Consolidated Entities [Domain] Allowance as a percentage of the ending total loan balance and accrued interest to be capitalized Allowance As Percentage Of Ending Loan Balance And Accrued Interest Allowance As Percentage Of Ending Loan Balance And Accrued Interest Income Statement [Abstract] Income Statement [Abstract] Entity Address, Address Line One Entity Address, Address Line One Name Forgone Recovery, Individual Name Amortization of Secured Borrowing Facility upfront fee Amortization of ABCP Upfront Loan Fees Amortization of ABCP Upfront Loan Fees Other adjustments to net income, net Other Noncash Income (Expense) Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Tier 1 Capital (to Average Assets) Banking Regulation, Tier 1 Leverage Capital Ratio, Well Capitalized, Minimum Tier 1 Capital (to Average Assets) Banking Regulation, Tier 1 Leverage Capital, Actual Without cosigner Without Cosigner [Member] Without Cosigner [Member] Allowance for Credit Losses Allowance For Credit Losses [Abstract] Allowance for credit losses. Beginning balance Ending balance Fair Value Disclosure, off-Balance-Sheet Risks, Amount, Liability Industry of Counterparty, Type [Axis] Industry of Counterparty, Type [Axis] PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Allowance Allowance [Abstract] Allowance. Effect of dilutive securities: Dilutive Securities, Effect on Basic Earnings Per Share [Abstract] Adjustment to Compensation: Adjustment to Compensation [Axis] Other Liabilities Derivative Liability [Abstract] Document Quarterly Report Document Quarterly Report Interest-bearing liabilities: Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Consumer Portfolio Segment Consumer Portfolio Segment [Member] Total interest expense Interest Expense, Operating 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 Accumulated other comprehensive loss (net of tax benefit of ($16,210) and ($24,176), respectively) Accumulated Other Comprehensive Income (Loss), Net of Tax Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Average common shares outstanding (in shares) Weighted average shares used to compute basic EPS (in shares) Weighted Average Number of Shares Outstanding, Basic Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] 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 Gross Unrealized Losses Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Total equity Beginning balance Ending balance Equity, Including Portion Attributable to Noncontrolling Interest U.S. Basel III Regulatory Requirements, Amount Banking Regulation, Tier 1 Leverage Capital [Abstract] Name Awards Close in Time to MNPI Disclosures, Individual Name 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 Gross Unrealized Losses Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Entity Filer Category Entity Filer Category Beginning balance, shares issued (in shares) Ending balance, shares issued (in shares) Shares, Issued Provision/New commitments - net Off-Balance-Sheet, Credit Loss, Liability, Credit Loss Expense (Reversal) Total Private Education Loans, gross, Year 1 Loans Gross, Originated In Current Fiscal Year Loans Gross, Originated In Current Fiscal Year 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 Statistical Measurement [Domain] Statistical Measurement [Domain] Gross Unrealized Losses Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] FICO Refreshed School FICO, Refreshed Amounts [Member] School FICO, Refreshed Amounts [Member] Available For Sale - Debt Securities Debt Securities [Member] Age Analysis of Past Due Loans Delinquencies Financing Receivable, Past Due [Table Text Block] Loan Restructuring Modification [Axis] Loan Restructuring Modification [Axis] Private education loan term accounted for as a secured financing Loan, Held-for-Sale or Securitization or Asset-Backed Financing Arrangement, Principal Outstanding Numerator: Numerator [Abstract] Numerator. Schedule of Notional Amounts of Outstanding Derivative Positions Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] All Trading Arrangements All Trading Arrangements [Member] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Change in fair value of future interest payments recorded in earnings Derivative Instruments Increase (Decrease) In Fair Value Of Future Interest Payments Recorded In Earnings Derivative Instruments Increase (Decrease) In Fair Value Of Future Interest Payments Recorded In Earnings Schedule of Earnings Per Share, Basic and Diluted Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Variable Interest Entity, Primary Beneficiary Variable Interest Entity, Primary Beneficiary [Member] Brokered deposit placement fee Cash Paid For Brokered Deposit Placement Fee Cash Paid For Brokered Deposit Placement Fee Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Derivative [Line Items] Derivative [Line Items] Student Loan Student Loan [Member] Total in percent Private Education Loans Gross, Percentage Private education loans gross in percent. Pay vs Performance Disclosure [Line Items] Total Private Education Loans in repayment Loans In Repayment, Before Allowance For Credit Loss Loans In Repayment, Before Allowance For Credit Loss Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Derivative [Table] Derivative [Table] Goodwill and acquired intangible assets, net Intangible Assets, Net (Including Goodwill) Schedule of Impact of Derivatives on the Consolidated Balance Sheet Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Number of mortgage-backed securities Debt Securities, Available-For-Sale, Number Of Positions Debt Securities, Available-For-Sale, Number Of Positions Deposits Deposit Liabilities Disclosures [Text Block] Other Performance Measure, Amount Other Performance Measure, Amount Expected amortization of 2026 Finite-Lived Intangible Asset, Expected Amortization, Year Three 670-699 FICO score 670-699 [Member] FICO score 670-699 [Member] Beginning balance (in shares) Ending balance (in shares) Common Stock, Shares, Outstanding Unrealized gains (losses) on investments OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment, before Tax 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 Fair Value Measurement Inputs and Valuation Techniques [Line Items] Fair Value Measurement Inputs and Valuation Techniques [Line Items] Accrued interest receivable not expected to be capitalized Accrued Interest Receivable Not Expected To Be Capitalized Accrued Interest Receivable Not Expected To Be Capitalized Accrued interest receivable Interest Receivable Cash Flow Hedges Cash Flow Cash Flow Hedging [Member] After one year to two years Time Deposit Maturities, Rolling Year Two Interest rate reduction Interest Rate Reduction, Percentage Interest Rate Reduction, Percentage Preferred stock, liquidation preference (in dollars per share) Preferred Stock, Liquidation Preference Per Share Entity Tax Identification Number Entity Tax Identification Number Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table] Banking Regulation, Regulatory Capital Requirement, Compliance [Table] With and without cosigners Cosigner [Member] Cosigner credit quality indicators that are developed and used internally by the company. Schedule of Finite-Lived Intangible Assets [Table] Intangible Asset, Finite-Lived [Table] Common stock repurchased (in shares) Common stock repurchased (in shares) Treasury Stock, Shares, Acquired Loans Held for Investment Loans Held for Sale Loans, Notes, Trade and Other Receivables Disclosure [Text Block] Total Private Education Loans, Year 1 Loans, Originated In Current Fiscal Year Loans, Originated In Current Fiscal Year Total Private Education Loan provisions for credit losses Financing Receivable, Credit Loss, Expense (Reversal), Commitments Financing Receivable, Credit Loss, Expense (Reversal), Commitments Treasury Stock Treasury Stock, Common [Member] 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 Equity Components [Axis] Equity Components [Axis] Income taxes receivable, net Income Taxes Receivable Available-for-sale investments at fair value (cost of $2,113,257 and $2,563,984, respectively) Estimated Fair Value Available-for-sale investments Debt Securities, Available-for-Sale 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 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 Interest Receivable Accrued Interest Receivable On Private Education Loans Accrued interest receivable on private education loans. Balance, beginning of period Balance, end of period Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Cash collateral pledged Derivative Asset, Subject to Master Netting Arrangement, Collateral, Obligation to Return Cash, Offset Against Derivative Asset Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] 2048 Maturity 2048 [Member] Maturity 2048 [Member] Investments [Domain] Investments [Domain] After four years to five years Time Deposit Maturities, Rolling Year Five Common stock repurchased Common stock repurchased, price Treasury Stock, Value, Acquired, Par Value Method Loans sold to third parties Continuing Involvement with Transferred Financial Assets, Principal Amount Outstanding Developed technology Developed Technology Rights [Member] Credit Loss [Abstract] Trading investments, cost Debt Securities, Trading, Amortized Cost Deferred tax asset Deferred Tax Assets, Net Less than 670 FICO score less than 670 [Member] FICO score less than 670 [Member] Weighted Average Weighted Average [Member] Total Private Education Loans Loans, Before Allowance For Credit Loss Loans, Before Allowance For Credit Loss 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] 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 Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-Sale [Line Items] Estimated Fair Value Debt Securities, Available-for-Sale, Unrealized Loss Position Accrued interest to be capitalized on loans in repayment Accrued Interest To Be Capitalized On Loans In Repayment Accrued Interest To Be Capitalized On Loans In Repayment 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 Equivalents, Restricted Cash, and Restricted Cash Equivalents Net amortization of discount on investments Accretion (Amortization) of Discounts and Premiums, Investments 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 Vertical risk retention interest Vertical Risk Retention, Percentage Vertical Risk Retention, Percentage Common stock held in treasury (in shares) Beginning balance (in shares) Ending balance (in shares) Treasury Stock, Common, Shares Derivatives recorded in interest expense Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount 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 Amount Interest-Bearing Deposit Liabilities, Domestic, by Component [Abstract] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] 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) Preferred stock, shares issued (in shares) Preferred Stock, Shares Outstanding 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 Transfers and Servicing [Abstract] Security Exchange Name Security Exchange Name Basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate 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 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 Reclassification out of Accumulated Other Comprehensive Income Reclassification out of Accumulated Other Comprehensive Income [Member] Derivative, fair value, amount offset against collateral, net Derivative, Fair Value, Amount Offset Against Collateral, Net Regulatory Capital Regulatory Capital Requirements under Banking Regulations [Text Block] Increase in accrued interest receivable Increase (Decrease) in Accrued Interest Receivable, Net 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. Compensation and benefits Labor and Related Expense Short-Term Short-term borrowings Short-Term Debt Less than 12 months Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract] Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Goodwill and Intangible Assets Disclosure [Abstract] Common stock, shares issued (in shares) Common Stock, Shares, Issued 2052 Maturity 2052 [Member] Maturity 2052 Decrease in income taxes payable, net Increase (Decrease) in Income Taxes Payable Secured borrowing facility maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Credit Cards Credit Cards [Member] Credit Cards Loans Financing Receivable, before Allowance for Credit Loss 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. Gross Unrealized Losses Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss Derivative liabilities Derivative values with impact of master netting agreements (as carried on balance sheet) Derivative instruments Derivative instruments Derivative Liability 2023-C SMB Private Education Loan Trust 2023-C [Member] SMB Private Education Loan Trust 2023-C Average contractual rate Financing Receivable, Change in Contractual Rate Financing Receivable, Change in Contractual Rate Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] 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 Common stock, shares authorized (in shares) Common Stock, Shares Authorized Total net derivatives Derivative Assets (Liabilities), at Fair Value, Net Transfers into level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 Adjusted Phase-In Amounts Remaining Cumulative Effect, Period Of Adoption, Adjusted Phase-In Amounts Remaining [Member] Cumulative Effect, Period Of Adoption, Adjusted Phase-In Amounts Remaining Brokered deposits Brokered Deposits Brokered Deposits Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] 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 Hedging Designation [Domain] Hedging Designation [Domain] 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. Income tax expense Deferred Income Tax Expense (Benefit) Less: amount of gain (loss) reclassified in interest expense Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax Fair Value Measurements on a Recurring Basis Fair Value, Recurring [Member] Estimated Fair Value Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer Decrease in other liabilities Increase (Decrease) in Other Operating Liabilities 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 Long-term borrowings Long-Term Long-Term Debt Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [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 Loan type Loan type Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Credit Quality Indicators [Domain] Credit Quality Indicators [Domain] Credit Quality Indicators [Domain] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Average purchase price per share (in dollars per share) Shares Acquired, Average Cost Per Share Credit Score, FICO [Domain] Credit Score, FICO [Domain] 2056 Maturity 2056 [Member] Maturity 2056 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 Interest expense on long-term borrowings Interest Expense, Long-Term Debt Private Education Loan term securitizations Private Education Loan Securitization [Member] Private Education Loan Securitization [Member] Acquired intangible assets amortization expense Acquired intangible assets amortization expense Amortization of Intangible Assets 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 2049 Maturity 2049 [Member] Maturity 2049 [Member] Accounting Policies [Abstract] Accounting Policies [Abstract] Liabilities Liabilities [Abstract] 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 Schedule of Certificates of Deposit Maturities Time Deposit Maturities [Table Text Block] Preferred stock dividends Preferred Stock Dividends, Income Statement Impact Current Fiscal Year End Date Current Fiscal Year End Date PEO Name PEO Name Percent of total notional derivative contracts Derivative Instrument, Percent Of Total Notional Derivative Contracts Derivative Instrument, Percent Of Total Notional Derivative Contracts Total Time Deposits All Award Types Award Type [Domain] Loan Restructuring Modification [Domain] Loan Restructuring Modification [Domain] 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 Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] 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 Non-PEO NEO Non-PEO NEO [Member] Useful Life (in years) Finite-Lived Intangible Asset, Useful Life 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 Available-for-sale investments Investments, Fair Value Disclosure Trading investments at fair value (cost of $43,373 and $43,412, respectively) Trading investments Debt Securities, Trading Additional Paid-In Capital Additional Paid-in Capital [Member] Hedging Relationship [Axis] Hedging Relationship [Axis] Schedule of Loans Held for Investment Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Schedule of Deposits Schedule Of Deposits [Table Text Block] Schedule of Deposits [Table Text Block] Class of Stock [Line Items] Class of Stock [Line Items] Recently Issued Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Class of Stock [Axis] Class of Stock [Axis] Weighted Average Cost of Funds (as a percent) Derivative, Basis Spread on Variable Rate Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Name Measure Name Entity Interactive Data Current Entity Interactive Data Current Private education loans sold Proceeds from Sale of Debt Securities, Available-for-Sale Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] Compliance with Regulatory Capital Requirements under Banking Regulations [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 Income taxes paid Income Taxes Paid 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] 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 Stock-based compensation expense Share-Based Payment Arrangement, Noncash Expense Debt Outstanding Debt, Long-Term and Short-Term, Combined Amount [Abstract] Cash disbursements made for: Supplemental Cash Flow Information [Abstract] Total non-interest income Noninterest Income 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 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] Net income (loss) attributable to SLM Corporation common stock Net Income (Loss) Available to Common Stockholders, Diluted Schedule of Impact of Derivatives on the Consolidated Statements of Income Derivative Instruments, Gain (Loss) [Table Text Block] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income [Domain] Increase in non-marketable securities Increase (Decrease) in Equity Securities, FV-NI 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 Schedule of Private Education Loan Portfolio Stratified by Key Credit Quality Indicators Financing Receivable Credit Quality Indicators [Table Text Block] Deposits Total deposits Deposits Total liabilities and equity Liabilities and Equity Dividends Dividends Subsequent Event Subsequent Events [Text Block] Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Net proceeds from sales of loans held for investment, capitalized interest Net Proceeds From Sales Of Student Loans Held For Sale, Capitalized Interest Net Proceeds From Sales Of Student Loans Held For Sale, Capitalized Interest Financial receivable, excluding accrued interest, modified, subsequent default Financing Receivable, Excluding Accrued Interest, Modified, Subsequent Default Hedging Designation [Axis] Hedging Designation [Axis] 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 Derivative Financial Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] 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 Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Credit Quality Indicators [Axis] Credit Quality Indicators [Axis] Credit Quality Indicators [Axis] Industry of Counterparty [Domain] Industry of Counterparty [Domain] Underlying Security Market Price Change Underlying Security Market Price Change, Percent Total Capital (to Risk-Weighted Assets) Banking Regulation, Total Risk-Based Capital Ratio, Well Capitalized, Minimum Measurement Input Type [Axis] Measurement Input Type [Axis] Individual: Individual [Axis] Debt Securities Debt Securities, Available-for-Sale, Measurement Input Shares repurchased related to employee stock-based compensation plans Share-Based Payment Arrangement, Decrease for Tax Withholding Obligation Private education loans at origination Private Education Loans At Origination Private Education Loans At Origination Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Statement [Line Items] Statement [Line Items] Measurement Input Type [Domain] Measurement Input Type [Domain] Unrealized loss, tax benefit OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment, Tax Financing receivable allowance period increase (decrease) Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease) Operating expenses: Operating Expenses [Abstract] Common stock, par value $.20 per share Common stock, par value $.20 per share [Member] Common stock, par value $.20 per share Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Allowance for Credit Losses Credit Loss, Financial Instrument [Policy Text Block] Loans held for sale Loan, Held-for-Sale, Fair Value Disclosure Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Minimum Minimum [Member] 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 Adoption Date Trading Arrangement Adoption Date Ending loans in repayment Allowance Coverage Of Charge Offs Ending Loans In Repayment Allowance coverage of charge-offs Ending loans in repayment. Tier 1 Capital (to Risk-Weighted Assets) Banking Regulation, Tier 1 Risk-Based Capital Ratio, Well Capitalized, Minimum 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 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] 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 Derivative Instrument [Axis] Derivative Instrument [Axis] Exercise Price Award Exercise Price 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 Tier 2 of government guarantee Tier Two of Government Guarantee Tier Two of Government Guarantee 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 Arrangement Duration Trading Arrangement Duration Tier 1 Capital (to Risk-Weighted Assets) Banking Regulation, Tier 1 Risk-Based Capital Ratio, Actual Goodwill and Acquired Intangible Assets Goodwill and Intangible Assets Disclosure [Text Block] Payment Default Financing Receivable, Modified, Subsequent Default Equity Equity, Attributable to Parent [Abstract] Deposits Deposits [Member] Estimated Fair Value Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months 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 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] Non-interest income: Noninterest Income [Abstract] Total investments Investments Derivative Asset, Statement of Financial Position [Extensible Enumeration] Derivative Asset, Statement of Financial Position [Extensible Enumeration] 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 Transfer - funded loans Off-Balance Sheet, Credit Loss, Liability, Writeoff Off-Balance Sheet, Credit Loss, Liability, Writeoff Total Private Education Loans, Year 3 Loans, Originated Two Years Before Current Fiscal Year Loans, Originated Two Years Before Current Fiscal Year 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 Extended Maturity Extended Maturity [Member] Tier 1 Capital (to Average Assets) Banking Regulation, Tier 1 Leverage Capital, Well Capitalized, Minimum Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Expected amortization of 2027 Finite-Lived Intangible Asset, Expected Amortization, Year Four All Individuals All Individuals [Member] Total Private Education Loans in Repayment, Year 1 Loans In Repayment, Originated In Current Fiscal Year Total loans in repayment. Entities [Table] Entities [Table] Other investments Other Investments After five years Time Deposit Maturities, after Rolling Year Five Loans held for investment (net of allowance for losses of $1,413,621 and $1,339,772, respectively) Private Education Loans, net Financing Receivable, Excluding Accrued Interest, after Allowance for Credit Loss Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Number of central counterparties Number Of Counterparties Number Of Counterparties Receivables [Abstract] Receivables [Abstract] 2026 Maturity 2026 [Member] Maturity 2026 Preferred Stock Dividends, Preferred Stock, Cash Gross Unrealized Gains Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax Financing receivable, excluding accrued interest, modified, charged off Financing Receivable, Excluding Accrued Interest, Modified, Charged Off Financing Receivable, Excluding Accrued Interest, Modified, Charged Off 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 Assets: Assets, Fair Value Disclosure [Abstract] 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 Liability Class [Axis] Liability Class [Axis] 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 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 Net position Derivative Liability, Including Not Subject to Master Netting Arrangement, after Offset and Deduction Valuation Approach and Technique [Axis] Valuation Approach and Technique [Axis] Number of government sponsored securities with unrealized losses Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions Cumulative Effect, Period Of Adoption [Domain] Cumulative Effect, Period of Adoption [Domain] Increase in other assets Increase (Decrease) in Other Operating Assets 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 Fixed-rate Fixed-rate Fixed Income Interest Rate [Member] Share Repurchase Program [Domain] Share Repurchase Program [Domain] Actual Ratio Banking Regulation, Risk-Based Information [Abstract] Impairment of intangible assets Impairment of Intangible Assets, Finite-Lived Proceeds from sales and maturities of available-for-sale securities Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale Commitments, Contingencies and Guarantees Commitments and Contingencies Disclosure [Text Block] Cash and cash equivalents Cash And Investments Interest Income Loss Cash and investments interest income (loss). Measure: Measure [Axis] Loss emergence period Loss Contingency, Loss Emergence Period Loss Contingency, Loss Emergence Period Asset Class [Domain] Asset Class [Domain] Common stock closing price (in dollars per share) Share Price Ending balance: collectively evaluated for impairment Financing Receivable, Allowance for Credit Loss, Collectively Evaluated Investments: Investments [Abstract] Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Issuance of common shares (in shares) Common shares issued (in shares) Stock Issued During Period, Shares, New Issues Entity Emerging Growth Company Entity Emerging Growth Company 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 Capitalized interest Loans Pledged As Collateral, Capitalized Interest Loans Pledged As Collateral, Capitalized Interest 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 Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Interest Rate Reduction Interest Rate Below Market Reduction [Member] 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 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 Equity Component [Domain] Equity Component [Domain] Preferred stock, par or stated value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Reconciliation of the Consolidated Statements of Cash Flows to the Consolidated Balance Sheets: Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents [Abstract] Net interest income after provisions for credit losses Interest Income (Expense), after Provision for Loan Loss Total interest income Interest and Dividend Income, Operating Unfunded Commitments Unfunded Commitments [Abstract] Unfunded Commitments Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Increase in tax indemnification receivable Interest Income On Tax Indemnification Receivable Interest Income On Tax Indemnification Receivable Entity Shell Company Entity Shell Company Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Loan delinquent 30-59 days 30-59 Days Past Due Financial Asset, 30 to 59 Days Past Due [Member] Statement [Table] Statement [Table] Measurement Frequency [Domain] Measurement Frequency [Domain] Significant Accounting Policies Significant Accounting Policies [Text Block] Schedule of Variable Interest Entities Schedule of Variable Interest Entities [Table Text Block] 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 Settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements Borrowings collateralized by loans in securitization trusts - issued Borrowings Collateralized By Loans In Trust Issued Borrowings Collateralized By Loans In Trust Issued Changes in operating assets and liabilities: Increase (Decrease) in Operating Assets [Abstract] Financing Receivable, Past Due [Line Items] Financing Receivable, Past Due [Line Items] Interest Interest Paid, Excluding Capitalized Interest, Operating Activities Ending balance: collectively evaluated for impairment Financing Receivable, Collectively Evaluated for Credit Loss Level 1  Fair Value, Inputs, Level 1 [Member] CME CHICAGO MERCANTILE EXCHANGE [Member] LCH London Clearing House [Member] London Clearing House [Member] Year 2 Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Allowance as a percentage of the ending loans in repayment and accrued interest to be capitalized on loans in repayment Allowance As Percentage Of Ending Loans In Repayment Allowance as a percentage of the ending loans in repayment. Proceeds from FFELP Loan claim payments Proceeds From Claim Payments Proceeds From Claim Payments 2047 Maturity 2047 [Member] Maturity 2047 [Member] Financial receivable, excluding accrued interest, modified in period, to total financing receivables, percentage Financing Receivable, Excluding Accrued Interest, Modified in Period, to Total Financing Receivables, Percentage Earning assets: Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Tier 1 Capital (to Risk-Weighted Assets) Banking Regulation, Tier 1 Risk-Based Capital, Actual Trading - Residual Interests Retained Interest [Member] Fees paid on Secured Borrowing Facility Net Increase (Decrease) In Upfront Loan Fees Net Increase (Decrease) In Upfront Loan Fees 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. Valuation Technique, Discounted Cash Flow Valuation Technique, Discounted Cash Flow [Member] Included in other comprehensive income Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) Total net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities After two years to three years Time Deposit Maturities, Rolling Year Three Credit Facility [Axis] Credit Facility [Axis] Long-term borrowings Long-Term Debt, Fair Value Entity Registrant Name Entity Registrant Name Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] 2024 Maturity 2024 [Member] Maturity 2024 Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Axis] 2044 Maturity 2044 [Member] Maturity 2044 [Member] Fair Value as of Grant Date Award Grant Date Fair Value Level 2  Fair Value, Inputs, Level 2 [Member] 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 Issuance of common shares Stock Issued During Period, Value, New Issues 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 Consolidation Consolidation, Policy [Policy Text Block] Restatement Determination Date: Restatement Determination Date [Axis] 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 Title of 12(b) Security Title of 12(b) Security Common stock, par value $0.20 per share, 1.125 billion shares authorized: 440.5 million and 438.2 million shares issued, respectively Common Stock, Value, Issued 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 Acquisition transaction costs, net Amortization of Acquisition Costs 2024-C SMB Private Education Loan Trust 2024-C [Member] SMB Private Education Loan Trust 2024-C Restricted cash Restricted Cash Restricted Cash and Investments Total loans and accrued interest amount securitized at inception Loan Amount Securitized Loan Amount Securitized Tier 1 Capital (to Average Assets) Banking Regulation, Tier 1 Leverage Capital Ratio, Actual 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 Loan sale reduction to provision Loan sale reduction to provision Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Loan Sold Deferment Loans In-school/grace/deferment Loans In-School/Grace/Deferment [Member] Loans In-School/Grace/Deferment 2043 Maturity 2043 [Member] Maturity 2043 [Member] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Financing activities Net Cash Provided by (Used in) Financing Activities [Abstract] 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 2024-B SMB Private Education Loan Trust 2024-B [Member] SMB Private Education Loan Trust 2024-B Certificates of deposit Interest-Bearing Domestic Deposit, Time Deposits Valuation Approach and Technique [Domain] Valuation Approach and Technique [Domain] Financial receivable, excluding accrued interest, modified, accumulated Financing Receivable, Excluding Accrued Interest, Modified, Accumulated Basic earnings per common share (in dollars per share) Basic earnings per common share (in dollars per share) Earnings Per Share, Basic Ending total loans, gross Allowance Coverage Of Charge Offs Ending Loans Allowance coverage of charge-offs ending total loans. Carrying Amount of Assets Securing Debt Outstanding Variable Interest Entity, Nonconsolidated, Comparison of Carrying Amount of Assets and Liabilities to Maximum Loss Exposure [Abstract] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Contractual obligation Contractual Obligation Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Interest expense on short-term borrowings Interest Expense, Short-Term Borrowings Share Repurchase Program [Axis] Share Repurchase Program [Axis] Expected amortization of 2024 Finite-Lived Intangible Asset, Expected Amortization, Year One Decrease in other interest-earning assets Payments for (Proceeds from) Other Interest Earning Assets Impact of master netting agreement Derivative Liability, Subject to Master Netting Arrangement, Asset Offset Common Equity Tier 1 Capital (to Risk-Weighted Assets) Common Equity Tier One Risk Based Capital Common Equity Tier One Risk Based Capital 2024-D SMB Private Education Loan Trust 2024-D [Member] SMB Private Education Loan Trust 2024-D 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. Savings Interest-Bearing Domestic Deposit, Savings Increments in which forbearance is granted Financing Receivable, Increments In Which Forbearance Is Granted Financing Receivable, Increments In Which Forbearance Is Granted Deferred origination costs and unamortized premium/(discount) Financing Receivable, Unamortized Loan Cost (Fee) and Purchase Premium (Discount) Preferred stock dividends paid Payments of Ordinary Dividends, Preferred Stock and Preference Stock Entity Address, City or Town Entity Address, City or Town Allowance for credit losses Allowance for credit losses Beginning balance Ending Balance Private Education Loans allowance for losses Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest Impact of master netting agreement Derivative Asset, Subject to Master Netting Arrangement, Liability Offset Tier 3 of government guarantee Tier Three of Government Guarantee Tier Three of Government Guarantee Investments, Debt and Equity Securities [Abstract] Investments, Debt and Equity Securities [Abstract] Business Acquisition [Axis] Business Acquisition [Axis] 2042 Maturity 2042 [Member] Maturity 2042 [Member] Schedule of Acquired Intangible Assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Allowance for Credit Losses Allowance for Credit Losses [Text Block] 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 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 (in years) Debt Instrument, Weighted Average Life Debt Instrument, Weighted Average Life 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] Deposits - non-interest-bearing Noninterest-Bearing Deposit Liabilities Loan delinquent, current Current Financial Asset, Not Past Due [Member] Liabilities: Liabilities, Fair Value Disclosure [Abstract] Series B Preferred Stock Series B Preferred Stock [Member] Document Fiscal Year Focus Document Fiscal Year Focus Common stock repurchased, amount Treasury Stock, Value, Acquired, Cost Method Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Retail and other deposits Retail And Other Deposits Retail And Other Deposits Total earning assets Total Assets, Fair Value Disclosure 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 Document Period End Date Document Period End Date 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 Asset Class [Axis] Asset Class [Axis] Private Education Loans Securitized In 2024 Private Education Loans Securitized In 2024 [Member] Private Education Loans Securitized In 2024 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 Insider Trading Arrangements [Line Items] Trading Activity [Axis] Trading Activity [Axis] 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 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 Document Transition Report Document Transition Report 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 Low income housing tax credit investments Investment, Proportional Amortization Method, Elected, Amount Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Entity Current Reporting Status Entity Current Reporting Status Retained Earnings Retained Earnings [Member] Percentage of FFELP loans insured and guaranteed (at least) Financing, Percentage of FFELP Loans Insured and Guaranteed Financing, Percentage of FFELP Loans Insured and Guaranteed U.S. government-sponsored enterprises and Treasuries U.S. Government-Sponsored Enterprises and Treasuries [Member] U.S. Government-Sponsored Enterprises and Treasuries Private Education Loans Securitized In 2023 Private Education Loans Securitized In 2023 [Member] Private Education Loans Securitized In 2023 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 2024-E SMB Private Education Loan Trust 2024-E [Member] SMB Private Education Loan Trust 2024-E Secured Borrowing Facility ABCP Borrowings [Member] ABCP Borrowings [Member] Loan delinquent 90 days or greater past due 90 Days or Greater Past Due Financial Asset, Equal to or Greater than 90 Days Past Due [Member] Financing receivable, modified, weighted average term increase from modification Financing Receivable, Modified, Weighted Average Term Increase from Modification 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 Write-downs arising from transfer of loans to held for sale Allowance for Loan and Lease Losses, Loans Sold Unrealized gain (loss) Debt Securities, Available-for-Sale, Unrealized Gain (Loss) Amount of variation margin included as settlement Amount Of Variation Margin Included As Settlement Amount Of Variation Margin Included As Settlement Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Total non-interest expenses Noninterest Expense Executive Category: Executive Category [Axis] Interest income: Investment Income, Interest and Dividend [Abstract] Statement of Income Location, Balance [Domain] Statement of Income Location, Balance [Domain] Purchases of available-for-sale securities Payments to Acquire Debt Securities, Available-for-Sale Company Selected Measure Name Company Selected Measure Name Additional proceeds from sale Additional Proceeds From Sale Of Debt Securities, Available-For-Sale Additional Proceeds From Sale Of Debt Securities, Available-For-Sale