Fair Value (Details Textual) (USD $)	Jun. 30, 2012	Dec. 31, 2011
Fair Value (Textual) [Abstract]
Contractual amounts of written financial guarantees and letters of credit	$ 18,520,000	$ 19,841,000

Contractual amounts of written financial guarantees and letters of credit.

No definition available.

Name:	subk_ContractualAmountsOfWrittenFinancialGuaranteesAndLettersOfCredit
Namespace Prefix:	subk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant