XML 44 R32.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Loans Held for Investment - Additional Information (Detail) | 9 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Sep. 30, 2017 | Dec. 31, 2016 | Jul. 01, 2006 | Jun. 30, 2006 | Sep. 30, 1993
Receivables [Abstract] |  |  |  |  |
Percent of private loans indexed to LIBOR | 78.20% | 81.40% |  |  |
Tier 1 of government guarantee (in percentage) | 97.00% |  | 97.00% |  |
Tier 2 of government guarantee (in percentage) |  |  |  | 98.00% |
Tier 3 of government guarantee (in percentage) |  |  |  |  | 100.00%
Estimated weighted average life of student loans (in years) | 5 years 7 months 3 days | 6 years |  |  |

X
- Definition Estimated weighted average life of student loans. + References No definition available. + Details
Name: | slm_EstimatedWeightedAverageLifeOfStudentLoans
Namespace Prefix: | slm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percent of Private Loans indexed to LIBOR + References No definition available. + Details
Name: | slm_PercentofPrivateLoansindexedtoLIBOR
Namespace Prefix: | slm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Tier One of Government Guarantee + References No definition available. + Details
Name: | slm_TierOneofGovernmentGuarantee
Namespace Prefix: | slm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Tier Three of Government Guarantee + References No definition available. + Details
Name: | slm_TierThreeofGovernmentGuarantee
Namespace Prefix: | slm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Tier Two of Government Guarantee + References No definition available. + Details
Name: | slm_TierTwoofGovernmentGuarantee
Namespace Prefix: | slm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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