Allowance for Credit Losses - Accrued Interest Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Receivables [Abstract]
Total Interest Receivable	$ 1,241,574	$ 1,187,123
90 Days or Greater Past Due	6,292	3,635
Allowance for Uncollectible Interest	$ 5,505	$ 4,937

Greater than ninety days past due accrued interest receivable.

No definition available.

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