Additional Proceeds from Sale of Debt Securities, Available-for-sale

No definition available.

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Namespace Prefix:	slm_
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Balance Type:	debit
Period Type:	duration

- Definition

Lendable value of collateral

+ References

No definition available.

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Loan Amount Securitized

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Residual Interest Percentage Of Facility Trust

+ References

No definition available.

+ Details

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Data Type:	dtr-types:percentItemType
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- Definition

Uncommitted Federal Funds

+ References

No definition available.

+ Details

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Namespace Prefix:	slm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Vertical Risk Retention, Percentage

+ References

No definition available.

+ Details

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Balance Type:	na
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- Definition

Amount of realized gain 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 https://asc.fasb.org/extlink&oid=126970911&loc=d3e27357-111563

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- 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

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Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of cash inflow from sale 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 11
-URI https://asc.fasb.org/extlink&oid=124260329&loc=d3e26853-111562

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 11
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3151-108585

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3179-108585

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- Details

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Balance Type:
Period Type:

- Details

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- Details

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- Details

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- Details

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Borrowings - Narrative (Details) - USD ($)			6 Months Ended
Borrowings - Narrative (Details) - USD ($)	May 27, 2022	Mar. 16, 2022	Jun. 30, 2022	Jun. 30, 2022	May 17, 2022	Dec. 31, 2021
Line of Credit Facility [Line Items]
Secured financings issued			$ 0	$ 0		$ 1,656,263,000
Vertical risk retention interest			5.00%	5.00%
Uncommitted federal funds			$ 125,000,000	$ 125,000,000
Lendable value of collateral			$ 2,100,000,000	$ 2,100,000,000		$ 3,300,000,000
ABCP borrowings \| Secured borrowings
Line of Credit Facility [Line Items]
Secured Borrowing Facility maximum borrowing capacity					$ 2,000,000,000
Residual interest percentage of facility trust					100.00%
2022-A
Line of Credit Facility [Line Items]
Vertical risk retention interest		5.00%
2022-A \| Student Loan
Line of Credit Facility [Line Items]
Private education loans sold		$ 973,000,000
Additional net proceeds from sales of loans held for investment, capitalized interest		95,000,000
Gain on sale		$ 10,000,000
2022-B
Line of Credit Facility [Line Items]
Vertical risk retention interest	5.00%
2022-B \| Student Loan
Line of Credit Facility [Line Items]
Private education loans sold	$ 2,000,000,000
Additional net proceeds from sales of loans held for investment, capitalized interest	107,000,000
Gain on sale	$ 11,000,000