Cover Page - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2023	Jan. 31, 2024	Jun. 30, 2023
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-13251
Entity Registrant Name	SLM Corp
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	52-2013874
Entity Address, Address Line One	300 Continental Drive
Entity Address, City or Town	Newark,
Entity Address, State or Province	DE
Entity Address, Postal Zip Code	19713
City Area Code	302
Local Phone Number	451-0200
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 3.7
Entity Common Stock, Shares Outstanding		220,349,715
Documents Incorporated by Reference	Portions of the proxy statement relating to the Registrant’s 2024 Annual Meeting of Stockholders are incorporated by reference into Part III of this Annual Report on Form 10-K.
Auditor Name	KPMG LLP
Auditor Location	McLean, Virginia
Auditor Firm ID	185
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Entity Central Index Key	0001032033
Common stock, par value $.20 per share
Document Information [Line Items]
Title of 12(b) Security	Common stock, par value $.20 per share
Trading Symbol	SLM
Security Exchange Name	NASDAQ
Floating Rate Non-Cumulative Preferred Stock, Series B, par value $.20 per share
Document Information [Line Items]
Title of 12(b) Security	Floating Rate Non-Cumulative Preferred Stock, Series B, par value $.20 per share
Trading Symbol	SLMBP
Security Exchange Name	NASDAQ