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v3.25.1

Significant Accounting Policies (Details) $ in Millions | 3 Months Ended
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Mar. 31, 2025 USD ($)
Accounting Policies [Abstract] |
Financing receivable, allowance for credit loss, period increase (decrease), change in estimate | $ (17)

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- Definition Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease), Change In Estimate + References No definition available. + Details
Name: | slm_FinancingReceivableAllowanceForCreditLossPeriodIncreaseDecreaseChangeInEstimate
Namespace Prefix: | slm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration