DIVIDENDS (Details) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($)
Number of previous years retained profit considered for dividend payment	2 years
Forecasted dividends in 2015
Dividends that could be paid without regulatory approval	$ 26,000

Represents the amount to be earned in the next fiscal year following the latest fiscal year before declaring dividends without approval of regulatory agency.

No definition available.

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