Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2017	May 08, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	MIDSOUTH BANCORP INC
Entity Central Index Key	0000745981
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		11,383,914
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q1
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2017