SUBSEQUENT EVENT - BRANCH CLOSURES (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012 item
Subsequent event \| Forecast
SUBSEQUENT EVENT - BRANCH CLOSURES
Number of branch offices to be closed	8
Proforma
SUBSEQUENT EVENT - BRANCH CLOSURES
Deposits of branch offices to be closed	88

Represents the number of branch offices of the entity, whose closure was approved by the board of directors.

No definition available.

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