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

Represents the monetary amount of Impaired Financing Receivable With and Without Related Allowance Recorded Investment, as of the indicated date.

No definition available.

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

Represents the monetary amount of Impaired Financing Receivable With and Without Related Allowance Specific Allowance, as of the indicated date.

No definition available.

Name:	smbc_ImpairedFinancingReceivableWithAndWithoutRelatedAllowanceSpecificAllowance
Namespace Prefix:	smbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the monetary amount of Impaired Financing Receivable With Related Allowance Specific Allowance, as of the indicated date.

No definition available.

Name:	smbc_ImpairedFinancingReceivableWithRelatedAllowanceSpecificAllowance
Namespace Prefix:	smbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of investment in impaired financing receivables for which there is no related allowance for credit losses.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 14A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953550-111524

Name:	us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of unpaid principal balance of impaired financing receivables for which there is no related allowance for credit losses.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (a)(4)

-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5212-111524

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Amount of investment in impaired financing receivables for which there is a related allowance for credit losses.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Unpaid principal balance of impaired financing receivables for which there is a related allowance for credit losses.

Name:	us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

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Data Type:	na
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