XML 14 R1.htm IDEA: XBRL DOCUMENT v3.21.1
Document and Entity Information - shares
3 Months Ended
Mar. 31, 2021
Apr. 20, 2021
Cover [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Mar. 31, 2021  
Document Fiscal Year Focus 2021  
Document Fiscal Period Focus Q1  
Trading Symbol MSCI  
Entity Registrant Name MSCI INC.  
Entity Central Index Key 0001408198  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Common Stock, Shares Outstanding   82,422,647
Entity Current Reporting Status Yes  
Entity Shell Company false  
Entity File Number 001-33812  
Entity Tax Identification Number 13-4038723  
Entity Address, Address Line One 7 World Trade Center  
Entity Address, Address Line Two 250 Greenwich Street, 49th Floor  
Entity Address, City or Town New York  
Entity Address, State or Province NY  
Entity Address, Postal Zip Code 10007  
City Area Code 212  
Local Phone Number 804-3900  
Entity Interactive Data Current Yes  
Entity Incorporation, State or Country Code DE  
Title of 12(b) Security Common stock, par value $0.01 per share  
Security Exchange Name NYSE  
Document Quarterly Report true  
Document Transition Report false