Fair Value Measurements and Disclosures (Details Narrative)	Dec. 31, 2018
Minimum [Member]
Percentage of estimated selling cost range	15.00%
Percentage of nonaccrual impaired loan write down range	80.00%
Maximum [Member]
Percentage of estimated selling cost range	20.00%
Percentage of nonaccrual impaired loan write down range	85.00%

Percentage of nonaccrual impaired loan write down range.

No definition available.

Name:	SGB_PercentageOfNonaccrualImpairedLoanWriteDownRange
Namespace Prefix:	SGB_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant