Name:	smbc_DebtSecuritiesReportedLessThanTheirHistoricalCostPercentOfInvestmentPortfolio
Namespace Prefix:	smbc_
Data Type:	num:percentItemType
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Period Type:	instant

Represents the monetary amount of Fair Value of Debt Securities Reported Less Than Their Historical Cost, as of the indicated date.

No definition available.

Name:	smbc_FairValueOfDebtSecuritiesReportedLessThanTheirHistoricalCost
Namespace Prefix:	smbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the monetary amount of Gain Recognized from Sales of Available for Sale Securities, during the indicated time period.

No definition available.

Name:	smbc_GainRecognizedFromSalesOfAvailableForSaleSecurities
Namespace Prefix:	smbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the monetary amount of Loss Recognized from Sale of Available for Sale Securities, during the indicated time period.

No definition available.

Name:	smbc_LossRecognizedFromSalesOfAvailableForSaleSecurities
Namespace Prefix:	smbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Carrying amount of assets sold under agreements to repurchase when the carrying amount (or market value, if higher than the carrying amount) of securities or other assets sold under repurchase agreements exceeds 10 percent of total assets.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(m)(1)(i)(A)(i))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

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Balance Type:
Period Type:

Name:	us-gaap_InvestmentTypeAxis=us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_InvestmentTypeAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	us-gaap_InvestmentTypeAxis=smbc_OtherSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: