XML 49 R36.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Investments - Narrative (Details) $ in Thousands | 3 Months Ended |
--- | --- | ---
Jun. 30, 2018 USD ($) security | Dec. 31, 2017 USD ($) security
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost | $ 185,749 | $ 247,607
Available-for-sale investments | 178,145 | 244,088
Ginnie Mae |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost | 72,000 |
Fannie Mae |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost | 49,000 |
Freddie Mac |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost | 46,000 |
Mortgage-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost | $ 167,203 | 227,607
Number of mortgage-backed securities sold | security | 9 |
Securities sold to align the portfolio with the Community Reinvestment Act requirements | $ 41,000 |
Available-for-sale investments | 160,416 | $ 225,047
Recognized loss on securities | $ 2,000 |
Number of mortgage-backed securities with unrealized losses | security | 75 | 62
Number of mortgage-backed securities | security | 84 | 92
Par value of mortgage-backed securities pledged | $ 161,000 | $ 218,000
Mortgage-backed securities | Ginnie Mae |  |
Debt Securities, Available-for-sale [Line Items] |  |
Number of mortgage-backed securities with unrealized losses | security | 35 | 31
Utah Housing Corporation bonds |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost | $ 18,546 | $ 20,000
Available-for-sale investments | 17,729 | 19,041
Moody's, Aa3 Rating | Utah Housing Corporation bonds |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost basis | $ 19,000 | $ 20,000

X
- Definition Debt Securities, Available-for-sale Securities Sold to Align With Community Reinvestment Act Requirements + References No definition available. + Details
Name: | slm_DebtSecuritiesAvailableforsaleSecuritiesSoldtoAlignWithCommunityReinvestmentActRequirements
Namespace Prefix: | slm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Number Of Mortgage-Backed Securities + References No definition available. + Details
Name: | slm_NumberOfMortgageBackedSecurities
Namespace Prefix: | slm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number Of Mortgage-Backed Securities Sold + References No definition available. + Details
Name: | slm_NumberOfMortgageBackedSecuritiesSold
Namespace Prefix: | slm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number Of Mortgage-Backed Securities With Unrealized Losses + References No definition available. + Details
Name: | slm_NumberOfMortgageBackedSecuritiesWithUnrealizedLosses
Namespace Prefix: | slm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Par Value Of Mortgage-Backed Securities Pledged To Federal Reserve Bank + References No definition available. + Details
Name: | slm_ParValueOfMortgageBackedSecuritiesPledgedToFederalReserveBank
Namespace Prefix: | slm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesAmortizedCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of realized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleRealizedLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | invest_InvestmentIssuerAxis=us-gaap_GovernmentNationalMortgageAssociationCertificatesAndObligationsGNMAMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | invest_InvestmentIssuerAxis=us-gaap_FederalNationalMortgageAssociationCertificatesAndObligationsFNMAMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | invest_InvestmentIssuerAxis=us-gaap_FederalHomeLoanMortgageCorporationCertificatesAndObligationsFHLMCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_MortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=slm_HousingCorporateBondsMemberMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_CreditRatingMoodysAxis=srt_MoodysAa3RatingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |