Fair Value Measurement - Schedule of Significant Observable Inputs Used in Fair Value Measurement of Level 3 Assets (Details) - Nonrecurring - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired loans	$ 14,880	$ 10,227
Other real estate	1,365	2,001
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Impaired loans	14,880	10,227
Other real estate	$ 1,365	$ 2,001

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.

No definition available.

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