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Documentation and Entity Information - shares
 9 Months Ended
Sep. 30, 2016
Nov. 09, 2016
Entity Registrant Name Interactive Brokers Group, Inc.  
Entity Central Index Key 0001381197  
Document Type 10-Q  
Document Period End Date Sep. 30, 2016  
Amendment Flag false  
Fiscal Year Focus 2016  
Fiscal Period Focus Q3  
Current Fiscal Year End Date --12-31  
Entity Well-known Seasoned Issuer Yes  
Entity Voluntary Filers No  
Entity Current Reporting Status Yes  
Entity Filer Category Large Accelerated Filer  
Common Class A    
Common Stock Shares Outstanding   67,982,963
Common Class B    
Common Stock Shares Outstanding   100