Fair Value Measurement (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount for selling costs (in hundredths)	10.00%msl_DiscountsForSellingCosts
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Period when new appraisals are received	28 days
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Period when new appraisals are received	42 days
Recurring [Member]
Available-for-sale securities [Abstract]
U.S. Government sponsored enterprises		$ 10,227
Obligations of state and political subdivisions	42,777	44,605
GSE mortgage-backed securities	104,788	109,103
Collateralized mortgage obligations: residential	131,167	60,839
Collateralized mortgage obligations: commercial	17,483	24,545
Other asset-backed securities		24,343
Collateralized debt obligation	1,352	1,218
Mutual funds	2,123	2,104
Recurring [Member] \| Level 1 [Member]
Available-for-sale securities [Abstract]
U.S. Government sponsored enterprises		0
Obligations of state and political subdivisions	0	0
GSE mortgage-backed securities	0	0
Collateralized mortgage obligations: residential	0	0
Collateralized mortgage obligations: commercial	0	0
Other asset-backed securities		0
Collateralized debt obligation	0	0
Mutual funds	2,123	2,104
Recurring [Member] \| Level 2 [Member]
Available-for-sale securities [Abstract]
U.S. Government sponsored enterprises		10,227
Obligations of state and political subdivisions	42,777	44,605
GSE mortgage-backed securities	104,788	109,103
Collateralized mortgage obligations: residential	131,167	60,839
Collateralized mortgage obligations: commercial	17,483	24,545
Other asset-backed securities		24,343
Collateralized debt obligation	1,352	1,218
Mutual funds	0	0
Recurring [Member] \| Level 3 [Member]
Available-for-sale securities [Abstract]
U.S. Government sponsored enterprises		0
Obligations of state and political subdivisions	0	0
GSE mortgage-backed securities	0	0
Collateralized mortgage obligations: residential	0	0
Collateralized mortgage obligations: commercial	0	0
Other asset-backed securities		0
Collateralized debt obligation	0	0
Mutual funds	0	0
Nonrecurring [Member]
Assets and Liabilities Measured on Nonrecurring Basis
Impaired loans	5,540	5,051
Other real estate	4,589	4,234
Nonrecurring [Member] \| Level 1 [Member]
Assets and Liabilities Measured on Nonrecurring Basis
Impaired loans	0	0
Other real estate	0	0
Nonrecurring [Member] \| Level 2 [Member]
Assets and Liabilities Measured on Nonrecurring Basis
Impaired loans	5,540	5,051
Other real estate	4,589	4,234
Nonrecurring [Member] \| Level 3 [Member]
Assets and Liabilities Measured on Nonrecurring Basis
Impaired loans	0	0
Other real estate	0	$ 0

No definition available.

Name:	msl_AssetBackedSecuritiesAvailableForSaleFairValueDisclosure
Namespace Prefix:	msl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

+ References

No definition available.

+ Details

Name:	msl_CollateralizedDebtObligationsAvailableForSaleFairValueDisclosure
Namespace Prefix:	msl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents securitized, pay-through debt securities collateralized by commercial real estate mortgage loans (mortgages) as of the balance sheet date which have been categorized as available-for-sale.

+ References

No definition available.

+ Details

Name:	msl_CollateralizedMortgageObligationsCommercialAvailableForSaleFairValueDisclosure
Namespace Prefix:	msl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents securitized, pay-through debt securities collateralized by residential real estate mortgage loans (mortgages) as of the balance sheet date which have been categorized as available-for-sale.

+ References

No definition available.

+ Details

Name:	msl_CollateralizedMortgageObligationsResidentialAvailableForSaleFairValueDisclosure
Namespace Prefix:	msl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Commission rate discount on sales with real estate agents.

+ References

No definition available.

+ Details

Name:	msl_DiscountsForSellingCosts
Namespace Prefix:	msl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents impaired loan receivable as presented on the statement of financial position which may include impaired mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts, or any other loans which are due the Company as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	msl_ImpairedLoansFairValueDisclosure
Namespace Prefix:	msl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

+ References

No definition available.

+ Details

Name:	msl_MutualFundsAvailableForSaleFairValueDisclosure
Namespace Prefix:	msl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Period when new appraisals are typically received.

+ References

No definition available.

+ Details

Name:	msl_PeriodWhenNewAppraisalsAreReceived
Namespace Prefix:	msl_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents bonds or similar securities issued by state, city, province, or local governments or their agencies in either the United States or a foreign country. Debt securities issued by state governments or provinces may include bond issuances of US state or foreign authorities. Debt securities issued by political subdivisions or US states may include debt issuances by county, borough, city, or municipal governments.

+ References

No definition available.

+ Details

Name:	msl_TradingInstrumentsObligationOfStateAndPoliticalSubdivisions
Namespace Prefix:	msl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

+ References

No definition available.

+ Details

Name:	msl_TradingInstrumentsUSGovernmentSponsoredEnterprisesDebtSecuritiesFairValueDisclosure
Namespace Prefix:	msl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_AvailableForSaleSecuritiesAbstract
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Details

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

- Definition

Fair value of securitized, pay-through debt securities collateralized by real estate mortgage loans classified as available-for-sale.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Mortgage-Backed Securities

-URI http://asc.fasb.org/extlink&oid=6517959

+ Details

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

- Definition

Fair value portion of other assets.

+ References

No definition available.

+ Details

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

- Details

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Namespace Prefix:
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- Details

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- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
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- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
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