Document and Entity Information - shares
9 Months Ended
Sep. 30, 2019
Oct. 21, 2019
Cover [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 30, 2019  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q3  
Trading Symbol MANH  
Entity Central Index Key 0001056696  
Current Fiscal Year End Date --12-31  
Entity Incorporation, State or Country Code 2Q  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Common Stock, Shares Outstanding   63,900,824
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Shell Company false  
Document Quarterly Report true  
Document Transition Report false  
Entity File Number 0-23999  
Entity Tax Identification Number 58-2373424  
Entity Address, Address Line One 2300 Windy Ridge Parkway  
Entity Address, Address Line Two Tenth Floor  
Entity Address, City or Town Atlanta  
Entity Address, State or Province GA  
Entity Address, Postal Zip Code 30339  
City Area Code 770  
Local Phone Number 955-7070  
Title of each class Common stock  
Name of each exchange on which registered NASDAQ