9. Deposits (Summary Of Maturity Distribution Of All Certificates Of Deposit) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013
Deposits
Three months or less	$ 53,212
Three through six months	23,785
Six through twelve months	82,135
Over twelve months	232,620
Total	$ 391,752
Three months or less, percentage	13.60%
Three through six months, percentage	6.10%
Six through twelve months, percentage	21.00%
Over twelve months, percentage	59.30%
Total, percentage	100.00%

Percentage Of Time Deposits 100000 Or More After 12 Months To Total Time Deposits 100000 Or More

No definition available.

Name:	smmf_PercentageOfTimeDeposits100000OrMoreAfter12MonthsToTotalTimeDeposits100000OrMore
Namespace Prefix:	smmf_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage Of Time Deposits 100000 Or More Six Months through 12 months To Total Time Deposits 100000 Or More

+ References

No definition available.

+ Details

Name:	smmf_PercentageOfTimeDeposits100000OrMoreSixMonthsThrough12MonthsToTotalTimeDeposits100000OrMore
Namespace Prefix:	smmf_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage Of Time Deposits 100000 Or More Three Months Or Less To Total Time Deposits 100000 Or More

+ References

No definition available.

+ Details

Name:	smmf_PercentageOfTimeDeposits100000OrMoreThreeMonthsOrLessToTotalTimeDeposits100000OrMore
Namespace Prefix:	smmf_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage Of Time Deposits 100000 Or More Three Months Through Six Months To Total Time Deposits 100000 Or More

+ References

No definition available.

+ Details

Name:	smmf_PercentageOfTimeDeposits100000OrMoreThreeMonthsThroughSixMonthsToTotalTimeDeposits100000OrMore
Namespace Prefix:	smmf_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage Total Of Maturity Distribution Of Time Deposits 100,000 Or More

+ References

No definition available.

+ Details

Name:	smmf_PercentageTotalOfMaturityDistributionOfTimeDeposits100000OrMore
Namespace Prefix:	smmf_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of contractual maturities of domestic and foreign time deposits (including certificates of deposits, individual retirement accounts and open accounts) in denominations of $100,000 or more, after twelve months from the balance sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 405

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6479006&loc=d3e64164-112818

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Industry Guide

-Number 3

-Section V

-Paragraph D

+ Details

Name:	us-gaap_ContractualMaturitiesTimeDeposits100000OrMoreAfter12Months
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

+ References

+ Details

Name:	us-gaap_ContractualMaturitiesTimeDeposits100000OrMoreSixMonthsThrough12Months
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

+ References

+ Details

Name:	us-gaap_ContractualMaturitiesTimeDeposits100000OrMoreThreeMonthsOrLess
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

+ References

+ Details

Name:	us-gaap_ContractualMaturitiesTimeDeposits100000OrMoreThreeMonthsThroughSixMonths
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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

- Definition

The aggregate amount of domestic and foreign time deposit liabilities (including certificates of deposits, individual retirement accounts and open accounts) in denominations of $100,000 or more.

+ References

+ Details

Name:	us-gaap_TimeDeposits100000OrMore
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant