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

Amortized cost excluding accrued interest, of financing receivable on nonaccrual status. Excludes net investment in lease.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-16

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

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-16

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Data Type:	xbrli:stringItemType
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Period Type:	duration

Percentage of financing receivable balance that is past due.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Amount of increase (decrease) in amortized cost of financing receivable modified for debtor experiencing financial difficulty.

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 33
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-33

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481933/310-10-55-12A

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of net investment in sales-type and direct financing leases, on nonaccrual status.