Related Party Transactions (Details Narrative) - USD ($)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Related Party Transactions [Abstract]
Shares held in ESOP and trust	256,225
Number of shares pledged	6,607
Aggregate indebtedness to bank	$ 1,079,000	$ 1,431,000
Loans from related parties	2,345,000
Repayment of loans	2,534,000
Directors and executive officers deposits	$ 2,072,000	$ 2,941,000

Directors And Executive Officers Deposits

No definition available.

Name:	SGB_DirectorsAndExecutiveOfficersDeposits
Namespace Prefix:	SGB_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Number Of Shares Pledged

+ References

No definition available.

+ Details

Name:	SGB_NumberOfSharesPledged
Namespace Prefix:	SGB_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Total current liabilities of the broker-dealer, less certain exceptions as defined.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Rule 15c3-1
-Number 240
-Section 15c3-1

+ Details

Name:	us-gaap_AggregateIndebtedness
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number of common stock held in a trust that has been set up specifically to accumulate stock for the sole purpose of distribution to participating employees but not yet earned.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 25
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=65888597&loc=d3e16701-113920

+ Details

Name:	us-gaap_CommonStockSharesHeldInEmployeeTrustShares
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Carrying amount as of the balance sheet date of obligations due all related parties. For classified balance sheets, represents the current portion of such liabilities (due within one year or within the normal operating cycle if longer).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(k)(1))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(a))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DueToRelatedPartiesCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

No definition available.

+ Details

Name:	us-gaap_RepaymentsOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration