Earnings/ (Loss) Per Common Share - Additional Information (Detail) In Millions, unless otherwise specified	Sep. 30, 2012	Sep. 30, 2011
Equivalent shares related to common stock options and common stock warrants outstanding were excluded from the computations of diluted income/(loss) per average common share because they would have been antidilutive	24	27

Securities as of the reporting date (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) in the future that were not included in the computation of diluted EPS because to do so would increase EPS amounts or decrease loss per share amounts for the period presented.

No definition available.

Name:	sti_AntidilutiveSecuritiesExcludedFromEarningsPerShareComputationAmount
Namespace Prefix:	sti_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant