FAIR VALUE - Valuation Inputs - (Details)	3 Months Ended
Mar. 31, 2016 item
FAIR VALUE.
Number of times a sample of prices supplied by the pricing agent is validated by comparison to prices obtained from other third party sources	2

Represents the number of times a sample of prices supplied by the pricing agent is validated by comparison to prices obtained from other third party sources.

No definition available.

Name:	msfg_NumberOfTimesInAYearSampleOfPricesSuppliedByPricingAgentIsValidatedByComparisonFromOtherThirdPartySources
Namespace Prefix:	msfg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration