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Concentrations of Risk (Details) | Dec. 31, 2024
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Risks and Uncertainties [Abstract] |
Percent of brokered deposit | 45.00%

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- Definition Brokered Deposit, Percent + References No definition available. + Details
Name: | slm_BrokeredDepositPercent
Namespace Prefix: | slm_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

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