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Concentrations of Risk (Details)	Dec. 31, 2024
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