XML 70 R53.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Significant Accounting Policies - Trading Investments (Details) | 1 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2020 | Dec. 31, 2021
Accounting Policies [Abstract] |  |
Vertical risk retention interest | 5.00% | 5.00%

X
- Definition Vertical Risk Retention, Percentage + References No definition available. + Details
Name: | slm_VerticalRiskRetentionPercentage
Namespace Prefix: | slm_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

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