Fair Value Accounting (Net Gains (Losses) from Fair Value Changes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Fair Value Disclosures [Abstract]
Mortgage loans held for sale	$ 2,516	$ (221)	$ (192)	$ 2,883

Changes in the fair value of mortgage loans held for sale that were included in the consolidated statements of income during the reporting period.

No definition available.

Name:	snv_ChangeInMortgageLoansHeldForSaleIncludedInNetIncome
Namespace Prefix:	snv_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration