Organization and Business - Additional Information (Detail)	Apr. 30, 2014 entity shares
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of publicly-traded entities \| entity	2
Number of shares issued for each share prior to spin-off (in shares) \| shares	1

Spin-Off, Number of Legally Separate Publicly Traded Entities

No definition available.

Name:	slm_SpinOffNumberofLegallySeparatePubliclyTradedEntities
Namespace Prefix:	slm_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant