Arrangements with Navient Corporation (Details) - USD ($) $ in Millions	Dec. 31, 2023	Apr. 30, 2014
Related Party Transactions [Abstract]
Remaining balance of indemnification receivable in connection with the spin-off	$ 0	$ 27

Deferred Tax Assets, Remaining Balance of Indemnification Receivable In Connection with The Spin-Off

No definition available.

Name:	slm_DeferredTaxAssetsRemainingBalanceofIndemnificationReceivableInConnectionwithTheSpinOff
Namespace Prefix:	slm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant