Acquisition (Details) (Federal Deposit Insurance Corporation [Member], Sunrise Bank [Member], USD $) In Millions, unless otherwise specified	May 10, 2013
Business Acquisition [Line Items]
Deposits assumed, including all uninsured deposits	$ 56.8
Loans [Member]
Business Acquisition [Line Items]
Loans acquired	$ 0.5

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits

No definition available.

Name:	snv_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedDeposits
Namespace Prefix:	snv_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant