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Significant Accounting Policies - Securitization Accounting (Details) | 12 Months Ended
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Dec. 31, 2021
Accounting Policies [Abstract] |
Asset balance related to securitization trust (as a percentage) | 10.00%

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- Definition Variable Interest Entities, Option to Exercise, Maximum Percentage of Assets to Original Loan Balance + References No definition available. + Details
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Namespace Prefix: | slm_
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Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
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Balance Type: | na
Period Type: | duration