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v2.4.1.9

Stockholders' Equity - Additional Detail (Details) (USD $) | 3 Months Ended
--- | ---
Mar. 31, 2015 | Mar. 31, 2014
Class of Stock [Line Items] |  |
Total net transfers from the entity that is now a subsidiary of Navient | $ 0 slm_NetTransfersToFromAffiliate | $ 17,244,000 slm_NetTransfersToFromAffiliate
Common Stock |  |
Class of Stock [Line Items] |  |
Common stock closing price (usd per share) | $ 9.28 us-gaap_SharePrice / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember |

X
- Definition Net Transfers (To) From Affiliate + References No definition available. + Details
Name: | slm_NetTransfersToFromAffiliate
Namespace Prefix: | slm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Details
Name: | us-gaap_ClassOfStockLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Price of a single share of a number of saleable stocks of a company. + References No definition available. + Details
Name: | us-gaap_SharePrice
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

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- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_CommonStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |