XML 84 R67.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Investments - Additional Info (Details) $ in Millions | 1 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Mar. 31, 2020 | Dec. 31, 2021 USD ($) security | Dec. 31, 2020 USD ($) security
Summary of Investment Holdings [Line Items] |  |  |
Number of mortgage-backed securities |  | 180 | 163
Par value of mortgage-backed securities pledged to FRB | $ |  | $ 888 | $ 815
Vertical risk retention interest | 5.00% | 5.00% |
Mortgage-backed securities |  |  |
Summary of Investment Holdings [Line Items] |  |  |
Number of government sponsored securities with unrealized losses |  | 60 | 14

X
- Definition Debt Securities, Available-for-sale, Number of Positions + References No definition available. + Details
Name: | slm_DebtSecuritiesAvailableForSaleNumberOfPositions
Namespace Prefix: | slm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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

X
- Definition Vertical Risk Retention, Percentage + References No definition available. + Details
Name: | slm_VerticalRiskRetentionPercentage
Namespace Prefix: | slm_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27290-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 4 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=124269663&loc=SL82922888-210455 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
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_SummaryOfInvestmentHoldingsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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