The fair value related to impaired financing receivables.

No definition available.

Name:	msfg_ImpairedFinancingReceivableFairValueDisclosure
Namespace Prefix:	msfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Gross carrying amount of investment of impaired financing receivables with related allowance for credit losses.

+ References

No definition available.

+ Details

Name:	msfg_ImpairedFinancingReceivableGrossCarryingAmount
Namespace Prefix:	msfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the amount of provision expenses for credit losses related to recorded investment.

+ References

No definition available.

+ Details

Name:	msfg_ImpairedFinancingReceivableRelatedProvisionExpenses
Namespace Prefix:	msfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of valuation allowance for credit losses related to gross carrying value.

+ References

No definition available.

+ Details

Name:	msfg_ImpairedFinancingReceivableValuationAllowance
Namespace Prefix:	msfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying amount as of the balance sheet date of other real estate and foreclosed assets after valuation allowance. Other real estate may include real estate investments, real estate loans that qualify as investments in real estate and premises that are no longer used in operations may also be included in real estate owned. Foreclosed assets include all assets obtained in full or partial satisfaction of a debt arrangement through foreclosure proceedings.

+ References

No definition available.

+ Details

Name:	msfg_OtherRealEstateAndForeclosedAssetsNet
Namespace Prefix:	msfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of increase (recovery) in valuation allowance applied to contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

No definition available.

+ Details

Name:	msfg_ServicingAssetAtAmortizedValueValuationAllowanceIncreaseDecrease
Namespace Prefix:	msfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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

- Details

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

- Definition

Amortized amount of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 50

-Section 25

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=7524895&loc=d3e120260-111741

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 50

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122492-111745

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 50

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 50

-Section 50

-Paragraph 4

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=7882072&loc=d3e122739-111746

+ Details

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

- Definition

Amount of valuation allowance applied to contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 50

-Section 50

-Paragraph 4

-Subparagraph (a)(5)

-URI http://asc.fasb.org/extlink&oid=7882072&loc=d3e122739-111746

+ Details

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

- Definition

Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 50

-Section 50

-Paragraph 3

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=7882072&loc=d3e122625-111746

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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FAIR VALUE (Details 4) (Non-recurring basis, USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Assets:
Total impaired loans	$ 1,206		$ 1,290
Impaired servicing rights	1,698us-gaap_ServicingAssetAtFairValueAmount		1,854us-gaap_ServicingAssetAtFairValueAmount
Other real estate owned/assets held for sale			462
Recorded investment of impaired loans	1,911		2,056
Valuation allowance of impaired loans	705		766
Provision expenses of impaired loans	129	(32)
Gross outstanding balance of servicing rights	2,098us-gaap_ServicingAssetAtAmortizedValue		2,254us-gaap_ServicingAssetAtAmortizedValue
Valuation allowance of servicing rights	400		400
Change occurred in the valuation allowance	0	0
Breakdown of properties by portfolio class
Other real estate owned/assets held for sale			462
Commercial and industrial
Assets:
Total impaired loans	167
Recorded investment of impaired loans	297
Valuation allowance of impaired loans	130
Farm
Assets:
Total impaired loans	54		55
Recorded investment of impaired loans	76
Valuation allowance of impaired loans	22
Construction and development
Assets:
Other real estate owned/assets held for sale			21
Breakdown of properties by portfolio class
Other real estate owned/assets held for sale			21
Other
Assets:
Total impaired loans	985		1,235
1-4 family
Assets:
Other real estate owned/assets held for sale			150
Breakdown of properties by portfolio class
Other real estate owned/assets held for sale			150
Other real estate
Assets:
Total impaired loans	985
Other real estate owned/assets held for sale			291
Recorded investment of impaired loans	1,538
Valuation allowance of impaired loans	553
Breakdown of properties by portfolio class
Other real estate owned/assets held for sale			291
Level 3
Assets:
Total impaired loans	1,206		1,290
Impaired servicing rights	1,698		1,854
Other real estate owned/assets held for sale			462
Breakdown of properties by portfolio class
Other real estate owned/assets held for sale			462
Level 3 \| Commercial and industrial
Assets:
Total impaired loans	167
Level 3 \| Farm
Assets:
Total impaired loans	54		55
Level 3 \| Construction and development
Assets:
Other real estate owned/assets held for sale			21
Breakdown of properties by portfolio class
Other real estate owned/assets held for sale			21
Level 3 \| Other
Assets:
Total impaired loans	985		1,235
Other real estate owned/assets held for sale			291
Breakdown of properties by portfolio class
Other real estate owned/assets held for sale			291
Level 3 \| 1-4 family
Assets:
Other real estate owned/assets held for sale			150
Breakdown of properties by portfolio class
Other real estate owned/assets held for sale			$ 150