Allowance for Loan Losses - Accrued Interest Receivable (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Receivables [Abstract]
Total Interest Receivable	$ 773,967	$ 542,919
Greater Than 90 Days Past Due	803	791
Allowance for Uncollectible Interest	$ 3,562	$ 3,332

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