LOANS, Aggregate Allowance for Loan Losses and Related Party Lending (Details) (USD $)	12 Months Ended
Dec. 31, 2014 Segment	Dec. 31, 2013	Dec. 31, 2012
Activity in allowance for loan losses [Roll Forward]
Beginning balance	$ 8,779,000	$ 7,370,000	$ 7,276,000
Provision for loan losses	5,625,000	3,050,000	2,050,000
Recoveries	738,000	265,000	300,000
Loans charged-off	(3,916,000)	(1,906,000)	(2,256,000)
Ending balance	11,226,000	8,779,000	7,370,000
Activity in related party loans and commitments to extend credit [Roll Forward]
Balance, beginning of year	3,114,000
New loans	407,000
Repayments and adjustments	(544,000)
Balance, end of year	2,977,000	3,114,000
Number of industry segment concentration above threshold limit	1
Threshold percentage of loan portfolio (in hundredths)	10.00%us-gaap_ConcentrationRiskPercentage1
Loans exposure in oil and gas industry	265,000,000msl_LoansExposureInOilAndGasIndustry
Exposure in oil and gas industry specified as percentage of total loans (in hundredths)	20.60%
Loans with exposure in commercial real estate	510,700,000
Loans on nonaccrual status	10,701,000	5,099,000
Commercial Real Estate [Member]
Activity in allowance for loan losses [Roll Forward]
Beginning balance	1,389,000	2,166,000
Provision for loan losses	699,000	(788,000)
Recoveries	407,000	29,000
Loans charged-off	(93,000)	(18,000)
Ending balance	2,402,000	1,389,000
Activity in related party loans and commitments to extend credit [Roll Forward]
Loans with exposure in commercial real estate	467,200,000
Percentage of CRE loans secured by owner-occupied commercial properties (in hundredths)	56.00%
Loans on nonaccrual status	$ 6,500,000
Nonaccrual status of loans specified as percentage of total CRE loans (in hundredths)	1.30%

This line item represents the exposure in the oil and gas industry specified as a percentage of total loans.

No definition available.

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- Definition

This line item represents the loans exposure in the oil and gas industry.

+ References

No definition available.

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This line item represents the loans with exposure in the commercial real estate section.

+ References

No definition available.

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- Definition

This line item represents the percentage of nonaccrual status of loans specified as percentage of total CRE loans.

+ References

No definition available.

+ Details

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- Definition

This line item represents the number of industry segment concentration above threshold limit of the loan portfolio.

+ References

No definition available.

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- Definition

This line item represents the percentage of CRE loans secured by owner occupied commercial properties.

+ References

No definition available.

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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- Definition

A valuation allowance for financing receivables that are expected to be uncollectible.

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- Definition

Amount of recovery of financing receivables doubtful of collection that were previously charged off.

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- Definition

Amount of direct write-downs of financing receivables charged against the allowance.

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- Definition

Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date.

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- Definition

For an unclassified balance sheet, reflects the carrying amount of unpaid loan amounts due from related parties at the balance sheet date.

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- Definition

Reflects the amount of new advances made to related parties in the form of loan and lease receivables.

+ References

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- Definition

Reflects the amount of collections received from related parties to reduce the carrying amounts of loans and leases receivable due from them.

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- Definition

Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

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