Allowance for Loan Losses - Accrued Interest Receivable (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Receivables [Abstract]
Accrued Interest Receivable On Private Education Loans	$ 445,710	$ 333,857
Greater Than 90 Days Past Due	443	1
Allowance For Uncollectible Accrued Interest	$ 3,517	$ 4,076

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