XML 65 R49.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Borrowings - Securitizations (Details) - USD ($) |  |  |  |  | 1 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | ---
Feb. 28, 2017 | Oct. 31, 2016 | Jul. 31, 2016 | May 31, 2016 | Mar. 31, 2018 | Nov. 30, 2017 | Dec. 31, 2017 | Dec. 31, 2016
Securities Financing Transaction [Line Items] |  |  |  |  |  |  |  |
Total Issued |  |  |  |  | $ 670,000,000 |  | $ 1,448,000,000 | $ 1,782,000,000
Total loan and accrued interest amount securitized at inception on-balance sheet term securitization |  |  |  |  | 744,917,000 |  | $ 1,606,804,000 | $ 2,107,042,000
2016-A |  |  |  |  |  |  |  |
Securities Financing Transaction [Line Items] |  |  |  |  |  |  |  |
Total Issued |  |  |  | $ 501,000,000 |  |  |  |
Weighted Average Life (in years) |  |  |  | 4 years 3 days |  |  |  |
2016-B |  |  |  |  |  |  |  |
Securities Financing Transaction [Line Items] |  |  |  |  |  |  |  |
Total Issued |  |  | $ 607,000,000 |  |  |  |  |
Weighted Average Life (in years) |  |  | 4 years 3 days |  |  |  |  |
2016-C |  |  |  |  |  |  |  |
Securities Financing Transaction [Line Items] |  |  |  |  |  |  |  |
Total Issued |  | $ 674,000,000 |  |  |  |  |  |
Weighted Average Life (in years) |  | 4 years 3 months 7 days |  |  |  |  |  |
2017-A |  |  |  |  |  |  |  |
Securities Financing Transaction [Line Items] |  |  |  |  |  |  |  |
Total Issued | $ 772,000,000 |  |  |  |  |  |  |
Weighted Average Life (in years) | 4 years 3 months 7 days |  |  |  |  |  |  |
2017-B |  |  |  |  |  |  |  |
Securities Financing Transaction [Line Items] |  |  |  |  |  |  |  |
Total Issued |  |  |  |  |  | $ 676,000,000 |  |
Basis spread on variable rate |  |  |  |  |  | 0.80% |  |
Weighted Average Life (in years) |  |  |  |  |  | 4 years 25 days |  |
2018-A |  |  |  |  |  |  |  |
Securities Financing Transaction [Line Items] |  |  |  |  |  |  |  |
Total Issued |  |  |  |  | $ 670,000,000 |  |  |
Basis spread on variable rate |  |  |  |  | 0.78% |  |  |
Weighted Average Life (in years) |  |  |  |  | 4 years 5 months 4 days |  |  |
LIBOR | 2016-A |  |  |  |  |  |  |  |
Securities Financing Transaction [Line Items] |  |  |  |  |  |  |  |
Basis spread on variable rate |  |  |  | 1.38% |  |  |  |
LIBOR | 2016-B |  |  |  |  |  |  |  |
Securities Financing Transaction [Line Items] |  |  |  |  |  |  |  |
Basis spread on variable rate |  |  | 1.36% |  |  |  |  |
LIBOR | 2016-C |  |  |  |  |  |  |  |
Securities Financing Transaction [Line Items] |  |  |  |  |  |  |  |
Basis spread on variable rate |  | 1.15% |  |  |  |  |  |
LIBOR | 2017-A |  |  |  |  |  |  |  |
Securities Financing Transaction [Line Items] |  |  |  |  |  |  |  |
Basis spread on variable rate | 0.93% |  |  |  |  |  |  |

X
- Definition Debt Instrument, Weighted Average Life + References No definition available. + Details
Name: | slm_DebtInstrumentWeightedAverageLife
Namespace Prefix: | slm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Loan Amount Securitized + References No definition available. + Details
Name: | slm_LoanAmountSecuritized
Namespace Prefix: | slm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Face (par) amount of debt instrument at time of issuance. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399 + Details
Name: | us-gaap_DebtInstrumentFaceAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The percentage points added to the reference rate to compute the variable rate on the interest rate derivative. + References No definition available. + Details
Name: | us-gaap_DerivativeBasisSpreadOnVariableRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_SecuritiesFinancingTransactionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_DebtInstrumentAxis=slm_Issuance2016AMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=slm_Issuance2016BMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=slm_Issuance2016CMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=slm_Issuance2017AMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=slm_Issuance2017BMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=slm_Issuance2018AMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |