Represents the monetary amount of Operating Lease Costs Classified as Occupancy and Equipment Expense, during the indicated time period.

No definition available.

+ Details

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

- Definition

Amount of lessee's right to use underlying asset under operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479041/842-20-45-1

+ Details

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

- Definition

Amount of increase in right-of-use asset obtained in exchange for operating lease liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 53
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479589/842-20-55-53

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (g)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-4

+ Details

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

- Details

Name:	srt_ConsolidatedEntitiesAxis=smbc_ConsolidatedBalanceSheetMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Namespace Prefix:
Data Type:	na
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- Details

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Namespace Prefix:
Data Type:	na
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- Details

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Premises and Equipment - ROU Assets and Lease liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024	Jun. 30, 2024
Operating leases right of use asset	$ 6,855		$ 6,855		$ 6,669
ROU assets obtained in exchange for operating lease obligations:				$ 734
Consolidated Balance Sheet [Member]
Operating leases right of use asset	6,855		6,855		$ 6,669
Consolidated Statement Of Income [Member]
Operating lease costs classified as occupancy and equipment expense (includes short-term lease costs)	$ 291	$ 294	$ 886	880
Cash Paid For Amounts Included In The Measurement Of Lease Liabilities [Member] \| Supplemental Disclosures Of Cash Flow Information [Member]
ROU assets obtained in exchange for operating lease obligations:				$ 2,445